Hi Joss,
Good advice, so I did contact Motability.
GCB is payable even after an insurance claim, the logic being , the fact you have had a repair ,even if it was your fault and you paid the £100 excess, it should mean the vehicle is in good condition, therefore very saleable, so the bonus is paid.
In the circumstances where the insurance company offer you the option of not doing a repair after a bump, (obviously minor), you could be jeopardising your future GCB.
So now we know!
Regards, wonky