Be wary of going to insurers who claim to specialise in policies for the over-50's. Most of them are no more than trading names for 'ordinary' insurers, so you'll still be dealing with Axa, Aviva, Hastings, LV, etc. even though the name on their website is something like 'OldFogiesOnTheRoad.com'
This might be worth a read:
https://www.moneysavingexpert.com/car-insurance/
(I stand by my recommendation of giving Post Office Insurance a try though. The last time I tried to find a better renewal quote than the one they offered me I spent nearly two full days researching deals. The best one I could find was exactly what they'd offered me in the first place!)