House Move gifted money: Purchase deposit vs pay off existing mortgage

Tommyjw

Hi all, just after some viewpoints on the below as might be missing something, over thinking it etc.

Selling flat (offer accepted past few days) , buying a house (looking as we speak, expect to make offer next 2 weeks). Fairly large gifted deposit being used for the purchase alongside my own savings / equity. 

Gift currently in parents ISA.

 Is there a better option out of:

A - standard use gift as part of purchase deposit to be collected when property purchase ready, subject to all solicitor checks, lender gifted deposit form etc

B - using gift money now to pay off current mortgage on flat (works out about the same coincidentally) . Would mean i sell my place mortgage free which may save time, but not sure if it means less gifted deposit forms though or if they'd see the money coming in and out and want all the same evidence anyway. Also note sure if this means I then dont count as a "gifted deposit" should my best choice be a lender who doesn't like it.

I'm leaning towards B if it means less paperwork/ worry about any lender gifted deposit query? But that could be wrong