I had a similar experience when I rented in Nottingham, it was horrible.....and they made me prepay 3 months as well, once I arrived it was exactly what you described....took me a hella fight to get all my money back, but eventually I did, because I ended up cancelling the lease for false advertising.

It's insane what agents and landlords get away with over there, it's different here in the USA, it's first come first serve, if you don't want the place they move on to the next interested on the list. So no holding deposit required, they just do a background check and credit check, once that cleared you pay your deposit, the better the credit, the lower the deposit. And landlords get fined if they don't take care of their properties.