Fortunately I haven't had to go through the "test" of whether an insurance company actually delivers in an effective and efficient way for decades but -
LV were brilliant when sons came home from Uni adding them on and taking them off our family car policy for very little money.
NFU Mutual are reported to be very good. I have used them and the customer service was excellent but they are expensive.
https://www.which.co.uk/money/insura...e-aqkx76z7t0vw
I'll be interested to hear who's had great service as there's a renewal coming up in a few months.
Andy.