Need some impartial advice as I've been so pee'd off with them for so long I fear I may have lost all perspective 
DP and I were with previous landlord for 10 years, 9 in a 1 bed flat then after DD was born we moved to a 2 bed with the same landlord (private company not individual).
Our initial agreement was 6 months followed by a months notice to leave. After we'd been in the 2nd flat 8 months we got a letter saying we should have signed up for a further 6 months and it was either commit to another 6 months or let them know we would be leaving. We did this and again at the end of the first year as we had no plans to move and were going to try and save for a deposit for our own place (which was going to take some time)
Out of the blue, just after we had signed up for another 6 months, DP got relocated with his work. Contacted landlord to say they would try to relet and if they could we would stop being responsible for rent from the day new tenant moved in and would just charge a £50 admin fee.
We moved (couple of hundred miles away) and had to return our keys by recorded delivery as landlord could not get anyone out to do a handover. I asked pretty soon afterwards when we could get our deposit back as we were quite stretched paying rent on 2 propertied at the same time. They said they could not do anything until the end of the tenancy. I asked if they could at least do the inspection to make sure everything was ok so at least we would be reassured that when we did get it back it would be the full deposit. They said no, they were not allowed to? and would have to call me to get my permission before they even entered the property.
Got a call 2 weeks back from my old neighbour to say someone had moved in on 13th Jan. A week later got an e-mail from my previous landlord to say they had let my flat and the last day we would be liable for the rent was 15th Jan. They said they had had to replace the front room carpet and would be charging me £288 for this as well as unspecified 'painting charges' and the £50 admin fee.
Carpet wasn't exactly clean - I was going to get one of those machines from the hire shop to give it a going over before we moved but it never happened, it was a thin cheap carpet in a tiny room though.
Today the check came through for £309, so £230 ish for the half a months rent we were due so only £80 left out of a £500 deposit????
Is there anything I can do to challenge this or am I going to have to accept its their word against mine? Am still sitting here fuming about 3 hours later 
Sorry for the long rant BTW 