To stop being polite about this

I can totally see how locals’ use of English is creating an integration barrier for you. Situations like this are usually about more than just the language. Do the locals have a different mindset than you? As a bilingual person living in the US and married to an American, I can attest that there are things I can say in my native language to other speakers of that language that I would never translate into English and vice versa. 80% of things are OK in both languages, but certain things just don’t sound right (PC?) in one or the other tongue. Could this be the reason why the locals prefer to stick to English with you?

It's rude, basically. You should reply to someone in the language they use to you - if it turns out after a couple of sentences that they are struggling, then fine, switch at that point.

@Valeriekat it’s still rude in that case. Think of it the other way round, If I was in London and encountered someone with a strong French accent and started speaking French to them, it would be like saying their English isn’t good enough. I don’t think there’s anything sinister in the OP’s case, it’s probably what they’re trained to do, but understand it’s a bit annoying.

Maybe they just want to improve their English?

As someone who has lived and worked in three foreign countries, I do not think you are wrong to feel offended. I suspect most of the people here saying as such have not lived many years abroad, especially in places in which they can't blend in with the local population. Xenophobia is growing around the world and often comes out in passive-aggressive gestures and micro aggressions. Dealing with it day after day is exhausting and painful. Your feelings are valid. Just keep speaking the local language and don't feel bad about telling someone you prefer not to speak English. It's not rude and you have every right to speak a language you have spent years learning to fluency.

Diolch dwi'n dysgu Cymraeg. Grateful for the parenting lesson there I never thought of that. I only speak my basic Welsh to the dog who doesn't respond to "Walkies" but does know Mynd am dro!

Ok you seem to have read my post completely wrongly.

White British people who live in Britain and have travelled to parts of Africa where swahili is spoken get very excited about speaking to them in swahili, when they’re from parts of Africa where swahili isn’t spoken. The only words they ( these African friends) are from The Lion King.

My friends have said it can be frustrating but they know it’s not coming out malice.

I suppose the difference is that they know they will always be “othered” but are fine with it.

It’s very common for people with blond/white skin to get preferential treatment in certain places where most people have dark skin. Part of it being welcoming. it’s easy to get used to that treatment, though. I’m speaking about it from personal experience.

Wow, the "practice their English" self-important patronising nonsense is still running rounds here.

The shop assistant doesn't know that the OP is British, she can be Nordic or central European. Especially in tourist areas, the experience is that many "foreign" people learn a few opening phrases and think they are thoughtful in doing so, but expect to be served in English.
The shop assistant is just going with the most probable scenario.

All the OP needs to do is "thanks, but I'm fine in X language" (in that language) and after some time her regular places will remember her.
And that's the easiest way to get over this "othering" - becoming known to the locals.

I think it's just part and parcel of living abroad. Id just reply in the local language "I'm cool with (Spanish), so could you point me to the cucumbers please?" Or whatever is relevant. Or like above, without making a thing about it, just reply in the local language.

I've been a blond woman in Spain. Brunette expat friends would get "Tia!" And stuff from people, I got the stilted English every time. Thems the breaks. Not gonna dye my hair and crack out the fake tan!

In the nicest of ways, OP, if this is annoying you this much, you are very lucky not to have far worse problems. You could try focusing on other things to calm your annoyance and redirect your energy towards things that matter more in the world.

That’s not what I said though. I was talking about an Italian woman living in London, speaking fluent English with an accent, getting tired of people always asking where she’s from.

I must have stated my reaction poorly. Just meant that I think it’s wise to bear in mind that a person like OP will rarely have experienced kneejerk alienation based on her skin tone, but I wasn't on about her own particular compatriots’ colouring wherever she is now.
Just a general observation about the genetic lottery, in a world which still prizes this over that, so to speak.

OP indicated the people in the country she's living are smaller and darker than her, but I don't think she indicated they weren't white? They may have as much white privilege as she does, so I don't think the argument about her inbuilt white privilege really stands up unless we know the people she's talking about are not white.

The stuff people have said to her on this thread about putting up and shutting up because she is not a local, not native, foreign, obviously "doesn't belong", etc, etc has been shocking and makes me wonder if this is the attitude they have towards people they encounter in the UK who look (to them) foreign, white or otherwise.

Bear in mind that fluent English is highly prized around the world in terms of tradeable skills, and it’s easy to see why others might grab the opportunity to practise with OP. She’s managed to emigrate after all, and maybe they hope to have a better chance themselves!
We really do have to concede that a blonde white woman has inbuilt privileges which open a lot of doors in all kinds of circs globally, and maybe a little dash of humility* on that score would cool the overheated attitude.

*not sure I’ve the exact word here: I mean sort of ‘anti-ego’, but suggesting no hint of apology for being as one is, IYSWIM.

She’d have got a kinder response from me if she wasn’t getting needlessly huffy with retail assistants who either believe they are helping out someone who looks to them like an obvious tourist or who want to practice English. I mean, I get why she finds it annoying, but unless these are people she sees every day, they don’t know she isn’t a tourist. It’s a completely normal facet of living in a country you’re not native to.

I think so too. Absurd reaction to a pretty universal experience in such circs, and an experience pretty much guaranteed to be motivated entirely benignly.
The locals have every right to react to a clearly non-native person such as OP with curiosity, and the attempts with English could just as easily be taken as a warm gesture of inclusion towards her, if she’d just reflect on the privilege she enjoys in living in that country, and adopt an attitude of gratitude (guaranteed to calm a person down).

Haha - yes, I'm not going to argue with that!

Maybe if the OP wasn't blond and British, a more sympathetic response would have been given here? The double standards when it comes to things like this are insane.

I agree. I've been shocked by some of the responses to OP on this thread.

Just say you don't speak English in their local language.

I’ve certainly had this too. I have an excellent ear for accents, and people often assume I have native or near-native fluency as a result. I have to explain that my Spanish is more Duolingo than ‘reading Cervantes in the original’.

An American friend of mine who has lived and worked in France for 25 years, married a French man and brought up their children there, and is fluent, obviously, is often slightly annoyed when shop assistants assume I’m the fluent one because my accent is better than hers, despite being far less fluent (though decent). I get her irritation! But it’s certainly not an unalloyed blessing.

I speak Brazilian Portuguese fluently, no accent apart from regional São Paulo. Whenever I’m in Portugal tho, they think I’m Brazilian so I end up explaining that I’m actually English

if I meet a Brazilian in Portugal, they’re just delighted to be able to speak to someone in our “normal” Portuguese 🤣🤣

This is very strange @Elconejorojo do you have a bit of a gringo accent? Is that what gives you away?

I did know an American in Brazil who was fluent, but had an American accent so if we were in a cab in an unfamiliar place he’d stay quiet so we didn’t get taken the looooong way round 🤣

It can also be a disadvantage to have a great accent but minimal proficiency! That was me in one foreign country... I'd say something and get a whole stream of unintelligible foreign language back.

In my experience, many French people fall into two groups - the ones who refuse to speak English, even though they are perfectly fluent, because they have a chip on their shoulder about the English and/or the English language. And the ones who will only speak English to you, and refuse to reply in French to your perfectly passable French, because you said some tricky sound slightly wrong and they are pretending they can't understand you.

You are obviously very bright to speak an additional language fluently.
Let it go and enjoy the mental challenge.

In shops in the UK you'd be lucky to get a good morning!

Your wish to not be seen by locals as foreign are unrealistic because that's what you are where you live. You will never be seen as local.

Your partner is local and has told you you're being rude. You might want to listen to him and let your resentment over something you can't change go.