issues with lodger

Is it that he's young, first time living away from home and just doesn't know how these arrangements work? Has he got the wrong end of the stick and thinks he's in a house share or some kind of tenancy? Really odd his GF walking into your personal space and commenting like that. I'd be making it clear next time she's round that you're the owner & landlady and he's the lodger.

Twice the bills, like water, council tax, gas, and electricity?

Or twice the mortgage, which is actually your asset, and he walks away with 0 asset?

Or twice of both?

”Yes, it’s much more spacious on the inside than it looks from the outside—one of the main reasons I fell in love with it and bought the house.”

I don’t know why people are being so dogmatic in either direction really. There are as many different lodger living arrangements as there are households. I have known people live in lodger set ups that didn’t look that different from house shares and others that absolutely were ‘you can have the kitchen for 20 minutes then you must creep soundlessly to your room and not come out, and definitely no guests.’
It’s why the interview and lodger agreement are so important, you have to make sure both sides know what they’re getting into and are on the same page about everything.
I have learnt from experience that people’s assumptions can be wildly off in both directions and you have to spell things out. My first lodger assumed she wouldn’t be allowed guests at all, ever, and asked me very tentatively after about 6 months, as if it was a massive favour, if it was ok if she brought a friend round for a quick coffee 😮

What did she say to you?

Bullshit.

I was a lodger before and we all sat around the kitchen. The owner had another lodger aswell. We all sat in the kitchen and living room. She didn't expect us to stay in our bedrooms

No place expects you to scuttle in and out of your bedroom quietly.

People make it up as they go along on here. Board and lodgings means food and accommodation.

Agreed - it’s “board and lodgings” if you want the benefit of being an equal resident then you pay equal bills and share a house.

To be fair the girlfriend coming in at will and lecturing the OP came out quite late until the thread!

And to be fair to the girlfriend and the lodger if the kitchen is the biggest room in the house and the lodger doesn't have his own kitchen then it would be generally reasonable to expect that he could sit and eat with a guest there. Not for him to have sole use, and not to be having an intimate conversation and not expecting the OP to not also be making use of the kitchen to prepare and eat food, and not to be making her feel uncomfortable for doing so.

Lodging is really a short term stop gap sort of thing, or week days only for those who live too far to commute to work.

It isn't the way many people live for years on end - except for those who genuinely are happy to go to work, come home, sit in their room with a microwaved meal all night and repeat day in, day out (they do exist, but they're not very common)

Very normal to have just your own bedroom with bed, desk, chair in it - use of the kitchen is normally a quick in and out, timed so as not to interfer with the home-owner.

It is not normal to assume, as a lodger, that you can sit around in the kitchen, taking your time or making complicated meals if the home-owner is also home/due home.

It is an easy deal for someone who doesn't mind their own company in the evenings, has plenty to do out of the house during the day, possibly isn't around at all at weekends, and wants a very cheap place to live.

Its not at all suitable for someone who wants communal living in a shared house/flat, where shared rooms are on a 'first come wins use of the room for as long as they want it' basis.

Does sound like OP's lodger has told, or allowed his girlfriend to think this is a house share and he is an equal house-mate.

You’re excused.

Maybe this is a 'starter lodger', and you'll go your separate ways and then choose somebody who is a better match, and agree clear ground rules right from the beginning. It has certainly been a learning experience so far!
My guess is that the ideal lodger would be a woman around your own age, someone with a reasonably busy working and social life, not WFH. She would either be single but not expecting to bring dates back to your place, or in a relationship with a partner who has their own space and who she can spend the night with. Spending the night at your place sometimes would have to be negotiated and you'd need to know and be comfortable with the partner first.
I think it would be quite reasonable to say that when they have visitors, the deal is that while the friends are in the communal spaces they make a bit of pleasant conversation with you, rather than only having intense conversations between themselves. They can take their food to eat in their own room if they want to be alone, and I think you need to fit a small table in their sitting room for this purpose, perhaps replacing the desk? And vice versa with your friends. You could also offer to let them know when you will be out for the evening so that they can have sole use of the kitchen then if they want, and vice versa.
I used to have lodgers years ago but I was much younger then and found it easier than I would now. It's quite a challenge; good luck with it.

It takes time; this is very new to OP!

OP, give him notice to go. You cannot be expected to school a grown adult in how to behave. If he's pushing boundaries in other ways this is going to get old very quickly. His friend felt comfortable talking down to you in your own home!! Just say that on reflection you don't think you're a good fit and tell him he has a week to find somewhere new. It's given you a chance to think about what rules you would like a new lodger to observe. Good luck, I hope you find someone suitable.

dearie me, did you not sort any paperwork at all ?

how often is his rent due ?
how far, if at all has he paid in advance ?

I would give him one month's notice.

as he has to find somewhere else, provide references, credit checks etc.

and if he finds somewhere sooner, then you are happy to allow him to leave earlier without having to pay his rent up to the end of the notice period.

Suddenly coming at him after the fact with all the terms and conditions is problematic, from my perspective. I'd feel like I'd moved in then you've moved the goal posts/changed the rules we discussed. I'd probably look at moving for something more secure and predictable.

I think it's okay to tell your lodger that he's your first lodger and you've learned that having a lodger isn't right for you at the moment. Explain that you recently lost your husband and have found you need the space alone while the grief is so fresh. (Make it about you, not him). Give him fair notice to find a new place. Then just treat it as a learning experience.

You are clearly regretting having a lodger, why on earth did you decide to do so ?

You yourself have only lived in the property 6 weeks ? and the lodger has been there 2 weeks ?

you have barely allowed yourself time to settle in, and get to know a new area as you say you chose to uproot yourself away from where you lived before, leaving behind all your friends.

Do you work ?

I asked earlier what notice period have you said either party needs to give ?