I used to be a painter many years ago to trade.
A couple of thousand is probably not that far off the mark for a proper company to do it right.
A job like that could take up to a week to do because of drying times.
You will probably be about £500 + just for paint depending on your spec. It’ll probably take more than two coats to do the walls right and the floor will need sealed, undercoated and then a finishing coat.
It’s costing so much because it’s a small job with a lot of traveling back and forward, if it was being done as part of say doing your whole house it would be a lot cheaper.
If i mind right you’re in Edinburgh, so you,ve the living in Edinburgh tax to pay.
If you can find a local one man band, i reckon it could be easily done for your budget.
best thing to do is DIY it really isn’t that hard.