My +4 has been with Peter Best, and my +8 with Gott & Wynne (because I needed class 1 business use which Peter Best couldn't arrange).
At renewal this year I intend to put the +4 with Gott & Wynne as well, if only because I can ring up and speak to one of the same two people each time and they know the cars. I also get European breakdown cover for £21 pa,(which I haven't had to test yet).
Haven't tried anyone else and apart from a windscreen chip, haven't needed to find out how good they really are!
Malcolm T