Thanks for that link -- it explains a lot.

"As a general rule, if you change your mind, the landlord can keep some - and perhaps all - of your holding deposit. The amount that the landlord can keep depends on the costs that the landlord has incurred because you changed your mind - for example, additional advertising costs and lost rent."

So does this mean that he can bill us for actual costs associated with renting the apartment, but not for anything else? The landlord has to give an itemized list? And presumably, if we find new tenants or if one of the other approved tenants wants to move in immediately, we could get back our whole holding deposit?