Can I take my sinking fund contributions with me when I move?

No, the contributions that you've made will remain for the benefit of the block and be used when works are required. You may wish to make an informal arrangement with your buyer to take this into account.

A buyer's solicitor will always write to L&Q and ask about the sinking fund balance. From experience, a sinking fund will improve the saleability of a property as the repair burden on the buyer is reduced.