M2014, yes I believe you can. Once you exchange contracts on a property and pay a deposit, it's sort of yours - that's why people suggest buyers get insurance in place upon settlement.
NB. I'm not an accountant.
Yep, you can still claim the cost.
I reckon the best time to do it is when the access is easy - tenants can slow things down sometime.
If you need to do some stuff to the property later, it can always be added to the Dep schedule.
Scott