New home, noisy neighbours late at night

[Magenta3]

Me and partner have moved to a new flat. We've been here a matter of weeks and our upstairs neighbours are REALLY loud. The building isn't brilliant for noise - hard floors, high ceilings etc. I can hear thumping footsteps up until around 2am EVERY night. Screaming, shouting, slamming doors..only saving grace is the thumping music has only been twice so far. I've said to my partner that I want to look for something else and move to preserve my sanity. Partner is getting hung up on the logistics - we'll lose the deposit for breaking the contract, we've only just unpacked, how do we know the next property won't be the same. I've lived with noisy neighbours before and when I politely asked them to be quiet they just retaliated and it got worse, slowly putting me on constant edge...these feelings are creeping back and I don't want to live like that again. AIBU to want to move so quickly?!

I don't think you are being unreasonable, but it is a bit of a predicament and your boyfriend isn't being unreasonable with his concerns.
Just because you've had bad relations with neighbours before, doesn't mean you will again. If you haven't met the people upstairs, it's worth trying to talk with them, and if it doesn't work, start planning your next move.

moving out would be a massive cost surely - it’s not just the deposit you’d lose, you’d have to pay for the full contract in most instances

I do sympathise though. My neighbours from hell seem to be moving out. They just decide to loudly move all their shit at 11pm every night but I can endure that