Re:
What are the circumstances behind them pulling out?
If it's simply that they've changed their mind, then I'd 100% keep 100% of the deposit.
If however they've lost their job or got a family illness etc then I'd suck it up and give them it all back.
As you've said, you can maybe get £1k more selling it to someone else anyway, so it could be a winner for you in the long run.
Karma may smile on you in the long run
What are the circumstances behind them pulling out?
If it's simply that they've changed their mind, then I'd 100% keep 100% of the deposit.
If however they've lost their job or got a family illness etc then I'd suck it up and give them it all back.
As you've said, you can maybe get £1k more selling it to someone else anyway, so it could be a winner for you in the long run.
Karma may smile on you in the long run