In Britain these days, the deposit is held by an independent agency, not the landlord or letting agent. They have to give a good reason to have money deducted - and you can then dispute this if it is spurious.

I recently moved, and the landlord (who was broke) was trying to keep money for all sorts of non-existent faults, most of which were due to his shoddy DIY work before I moved in. I raised a dispute and eventually got the vast majority of the money back. Just make sure you keep pictures of the state of the house before you move your stuff in.