I pay pennies for my car insurance (not sure why TBH) but the likes of Chris Knott and all the 'specialist' brokers have never been anywhere near competitive for me. Hundreds of pounds more each year. They all seem to use 'Highway' as the underwriter IME.
I am with whoever is cheapest that year for all our cars; generally Hastings and Churchill are competitive for us. It was LV for years, but they have decided we are not their market anymore, so have priced themselves out.
Even my 19 year old daughter's renewal on a Mini Cooper is only £400 this year. She only got her full licence last year!
Having read literally hundreds of posts on various car forums regarding insurance, I have concluded that there is no rhyme or reason to it. EVERYBODY'S risk is completely different.
The insurance database holds much more information about us than it used to (where do you think all the data being collected by everything we do online and on phones is going?) They know what you eat (loyalty cards), what your habits are. They know what type of music you like (youtube, alexa type things are constantly gathering information).
Selling personal information is BIG business. Insurance databases buy this information and use it to assess your premium. It's much more useful to them than what car you drive. NCB is a waste of time these days too. The insurance companies don't ask for proof of NCB; it's there in front of them, as they share information via the databases.
Insurance is one big cartel IMO; they decide who wants what business and divide it up among themselves by the premiums they charge.
So asking other people who is cheapest for their insurance, means absolutely nothing for your 'risk'.
I am not a conspiracy theorist by any means, but do believe the insurance industry is a conspiracy.