Yes, agree the onus is now on the landlord to prove it isnt as you took it on, and he is trying to pull a fast one.
My DS and friends have been in dispute about their deposits from uni house since June, the agency was stating it was retaining all but £30 each (out of £200) to be kept for, amongst other things, new mattresses, quoting that bottom of mattresses were stained (DS and friends had photos of stained mattress tops, but not bottoms, funnily enough!!!!)
The agency told them 'accept our offer, or get nothing'. I presume that they try that on with lots of people, not realising mine was being guided by me, as his friends were. I fight anything!!!
They have now gone to dispute and have just got 167 back each immediately. The remainder has now gone to arbitration - the agency is saying there is damaged skirting board, there were apparently builders in the house doing work when the agency photos were taken, after DS and friends moved out, so I can't see them getting away with that but we will see.
I have been shocked at how much the agency tried it on, the students took loads of photos at start and end but the agency have basically fought over anything that a photo wasn't taken of. Very very nasty. All respect to DS and his friends who wouldn't accept the reduction and have/are still fighting it.
DS is on placement this year, again in a shared house, I am sure he will have learnt a lesson and take pics of everything on the day they move out. He took photo of mattress bottom early on, when he knew about dispute on uni house.
Keep in touch with the deposit scheme and go to arbitration if necessary.