I think it’s a no lose situation.
I Would bonus hunt on £10/£20 spins maybe try get 2/3 bonuses until your balance hits £1k.
withdraw and make sure it comes through and then once it’s in your bank open up the games and hope the bonuses are still there. If they’re not you’ve not lost anything anyway. If they are happy days.
if they stop your withdrawal because of pending bonuses just say you didn’t realise and can they cancel them so you just withdraw your £1k.
cant see any way you end up not with £1k and a free shot at a few bonuses 