IME most student landlords are only in it for profit, & for getting as much money as they can
There probably are honourable exceptions, but they're hard to find.
having photos of the state of the place is a good start, & landlords do have to protect the deposit with \link{http://www.direct.gov.uk/en/HomeAndCommunity/Privaterenting/Tenancies/DG_189120\a TDS}, but although student rents are so high landlords still appear to think they can pocket the lot & then charge for eg annual repainting out of the deposits
DS1 shares with 5 others in Newcastle. Their annual rent last year was over £23,000, & they worked very hard to clean the house before they left, but the landlord is still intending to keep most of the deposit for professional cleaning & a coat of magnolia throughout 
The landlord's agent said there's no point appealing to the tribunal (??? or whatever it's called) because "they always find in favour of landlords", which has made him determined to push it as far as he can!
Good luck with yours, NQSD. (The mattress etc sounds disgusting
)