Some very good points on here. Another consideration is the rental company. What have they suggested as rental income ? Have they a good track record etc. I realise that the market as been poor to miserable this year however i do know quite a few complex's within bansko that have been renting well into and above the amount you require.
I would say do your homework 3 times over before making a decision.
Buy to let is dead all across the board. Plus u are buying in a market which has still got a considerable way to fall.There is no rational expectation of a £4k income in these financial times.Forget it for now is the logical move.
remember realistically you only get about 12 weeks of bookings in the season if things go well.. dont hold out for much else for the rest of the year..