Friends have told me not to declare them but, that’s not the kind of person I am.
Do not listen to your friends. Declare everything, especially at your age.
There is a thread running on another forum where a 60-something had a total loss accident, no fault of his.
Due to not declaring he had some exterior plastic 'bits' on his car, his insurance have cancelled his policy and won't entertain the claim (no fault claim BTW). The only way he can possibly be paid out is by going down a legal route. And he has had his policy cancelled so it will be very, very expensive to get insurance again, even at his age.
It's just not worth the risk.