Looking for a last minute break next week and came across a one bed place which looked ideal for me and DH for a few days. Went to the booking page and the price nearly doubled - apparently there's a £200 deposit (which wasn't mentioned anywhere in the particulars) which would be refunded 14 days after.
We usually go away in the UK 2/3 times a year and I've only been asked for significant damage deposits once - for a ten bed house, so that seemed totally reasonable. And others I've paid have been in the region of £50.
I dropped a note to the owner to say I wouldn't be booking and why. Would this have put you off too? It just seems a bit greedy to me. Rental deposits are protected in law but I don't know if there's anything similar for short term lets. Also the fact it wasn't mentioned until booking just seems a bit snaky.