An insurance company is only as good as when you need to make a claim. Having had an Admiral policy in the past (bought based on cost alone), when I actually needed help (somebody drove into me) they were a complete nightmare to deal with and I was left significantly out of pocket. I was constantly chasing and navigating Red tape, loopholes and penalties were put on me & my policy based on somebody else's actions. After reading the small print these penalties were Admiral specific and not a general insurance penalties.
Compare that with Aviva, who my ex's car was insured with, and when she made a claim in an accident she caused, the difference was Biblical. Aviva were very hands off, super efficient, and great comms.
I go with Ageas. They are c10% more than the cheaper quotes, but the level of cover is much better and should the worst happen the small print T&C's are on my side.
You get what you pay for.