I look at the underwriter rather than the broker.
Markerstudy are on the do not touch list.
Ageas & Aviva are preferred. Neither sell bike insurance direct so you have to go via a broker
If a broker is shit you can always go direct to the underwriter. You really do not want to be covered through a Markerstudy broker (C Nash, Swinton et al) and have a policy underwritten by them as well.
https://www.markerstudygroup.com/who-we-are/our-brands/ - scroll down to see the 40+ brands they own