UK Landlord Forum / Life

I have just found out my error and have taken immediate steps to rectify it, but I'm really stressed that it won't make any difference. I rented my home out three years ago, when I moved away for work and now I'm back, so I served two months notice. Tenants moved out on time but have broken tenancy agreement several times, ignoring my warning that they mustn't decorate or change fixtures and fittings and even withheld rent one month when I was carrying out essential repairs to a leaking pipe (which inconvenienced them). The oven and other appliances were left filthy, the kitchen door and hall carpet were removed  she even replaced my mattress without telling me and has had prepayment meters installed (£190 to have them removed). They've burned one of the carpets and ruined the cushions, also decorated both bedrooms.

I have a copy of the letter and the agreement, which states what was not permitted and I've taken photos of the damage. However, when I suggested to her that I would need time to work out how much this was all going to cost me and deduct it from the deposit, she is up in arms, saying she'll take me to court and she's not liable for wear and tear. So after looking into my rights, I discover that I've not complied with the regulations and wonder, does this negate my rights to the deposit? If the sheriff court gets involved (I'm in Scotland btw) are they most likely to apply the full sanction (3 x deposit) or should it depend on whether I have a case for deducting anything from this deposit in the first place? I realise that nobody can predict what a sheriff may do, but any advice would be greatly appreciated. 

How much is the deposit and how much is the damage?