Is it easier just to give the deposit back???

Tenancy Deposits

Your original agreement should be fine so you can unprotect the deposit with MyDeposits, and tick the box to state you are withholding all the deposit for damages. It's up to the tenant to open any dispute, so you'll have to wait and see if they do. At least you have photos even if they aren't signed by X (hopefully they have the dates on them!). Keep all receipts which relate to the cost of making good the room. (Did you take photos when X left?). Because of the way they left I hope you are lucky and never hear from them again. (By the way ignore X's girlfriend's mum, it's nothing to do with her).