I’ve messed up with the holiday I’ve booked

Why £900? I checked out this mountain warehouse and found for £50 or £100. Or buy elsewhere. I don’t think people are suggesting you spend that amount!

I went to Copenhagen in February and it was lovely. Cold but I just wrapped up. And Tivoli was open!

In your OP you asked “what do I do?” People on here are giving you advice and suggestions and you’re just hitting back with “I can’t afford to buy a second hand coat and sell it in for a loss” and “they look ugly and bulky.”
Just cancel the holiday if it’s this complicated for you.

Same thought. I mentioned the raincoat not being sufficient but it seems op disagreed with me. I don’t get complaining about cold weather and then wearing a raincoat. Raincoats are just waterproof nothings.

Why are you on here asking for advice when you’re ignoring everyone that’s trying to help you?

A raincoat will not suffice. Even with layers. If it genuinely goes down to -30 you NEED a ski coat. Simple as that.

As I’ve already said, and so have others, google mountain warehouse. It’s cheap. It usually has a sale. You can absolutely still use the coat in the UK in winter. 🤦🏻‍♀️

I went to Iceland in February, it was three foot deep in snow and cold but I never once felt overly cold.

I wore fleecy/thermal leggings under cheap Aldi ski pants, I bought a large fleecy hoody and wore a vest too and either a thin thermal layer or thin wool jumper then the hoody and my normal waterproof, windproof winter parka coat with wool hat, wool scarf, ear muffs and ski gloves. I bought cheap ski/snow boots from Aldi too. I still get the ski stuff out to wear as an outer layer in the snow here so it wasn’t wasted, and was quite cheap (less than £30 for the boots, glove and pants).

I had a holiday in Canada. At that time of the year it should have been around 0°. In reality they had a nasty cold snap and it was -40°.

We all wrapped up in layers with scarves and gloves and had some great skiing regardless.

It is not going to be -30C in Oslo during the daytime in March. I don’t know where you read that, but it is wrong.

Honestly, buying appropriate cloths should be part of your holiday budget
Im guessing OP has clothes that she wears in winter. They will do.
She is going to a city which admittedly gets cold but she's not on a polar expedition.
Oslo is quite a compact city and she will be going from building to building. Ive not spent long in Helsinki but that too is a capital which will be places of interest to go in and visit.
Too many clothes and she is in danger of over heating at the rate she is talking.
Seriously OP, calm down.

To be honest, id be more bothered about my budget than my clothes!

Honestly, buying appropriate cloths should be part of your holiday budget.
If you were going on a sunny holiday you’d buy a bikini and sunscreen. Some women are so heavy chested that they have to buy an expensive bikini. A thick ski coat on Vinted can be sold on again for a similar price.

Are you aware that food and drink is very expensive there? Do you have money for that? It sounds like you just didn’t think about your budget for the rest of the holiday after your flights and accomodation when you booked it.

i can’t afford to spend silly money on a coat that I then have to sell on at a loss.
I honestly think you are getting yourself worked up and making it a bigger deal than you need to.
Sure its going to be cold,but Ive had colder winter here than I have in Norway in February seriously.
Your puffer coat will be fine its you putting a block on that by saying it makes you look big. It may well do but so what, it'll keep you warm without having to buy another one.
The only time ive been so cold in the winter months when I've been abroad was in Serville!

Ive been fine in my Montane soft shell and a bob hat in Norway, I didnt need gloves.

Anyway have you looked on Vinted, I swear you can get a winter coat on there cheaper than a cocktail at the Hard Rock cafe in Oslo!

Leave the raincoat at home. Get a thick down jacket, or thick ski jacket.
also, just wear ski trousers over your thermals. More comfortable (and warmer) than wearing jeans.

This is silly. It would also have been silly if it was -5. Temperatures are always going to be colder there than in the UK. Get a proper coat on Vinted and sell it again afterwards if you’re not going to wear it in the UK. Get some thermal underwear and warm shoes /boots.

Go and enjoy it. Embrace it. Dress appropriately and you will have the most amazing time. They are both fabulous cities. What an opportunity.

Get ski style stuff, we went to finalnd in Feb and it got down to -30 but it was unusually cold, I doubt you'll actually get that cold. We were out in it all day enjoying activities. You need;
Thermal Base layer (polyester or merino wool)
Mid layer - fleeces, fleece lined leggings or joggers, wooly jumpers etc
Outer layer - get a ski coat and some thermal soft shell trousers
Ski socks
Gloves
Snood
Hat
Hand warmers
Thermal boots
Break the day up with lots of coffee shops And inside museums it'll be heated anyway.
Enjoy the holiday! You might get some beautiful snow etc.

I don’t think you’ve messed up, it will be cold but you can do/see all that.

I used to live in Oslo. You'll be fine, just bring a good coat.

Oh my gosh we were in Chicago in late March and it was bitterly cold, positively arctic! Just goes to show as you say you have to be prepared for a range of possibilities!

(I’ve also been in Norway in late March sitting outside eating ice cream in the sunshine!)

For -30 get a ski coat

I cannot emphasise that enough. I went skiing in -29 wearing base layers and my friends THICK down jacket, with gloves and sallopettes and it is the only time I’ve ever felt the cold. While my body was ok, my extremities were freezing, even in my usual ski gloves.

The ski coats are designed to keep that cold air out and your own heat in. Even though they don’t look any thicker, they work.

Waterproof walking shoes are fine with thick socks. You don’t need posh expensive base layers, Aldi and Lidl do them. Grab one of those fleece jumpers as well, then a ski coat on top. Have up to 3 base layers for under your fleece layer, you may not need them all. Get salopettes just in case. I only use one legging base layer under those. You can even get the thermal leggings and tops from Primark, they work fine.