Peter James seem OK for some with older bikes, but whenever I have tried them with a new-ish bike they are way out & admit that they are not competitive on modern bikes.
I went with Hastings when I first got the Interceptor as they were hundreds cheaper than Carole Nash who I was with at the time - the stupidly high premium CN quoted was apparently because the bike was "too new". After 2 years with Hastings I am back with CN again - premiums similar (CN were actually a bit more) but the CN policy covers my MZ and includes UK & EU breakdown & recovery.
MCN have an online "Go Compare" type premium generator that can get you some idea of premiums from many brokers with only having to fill out one online form. Make sure you check the "don't ring me" box or the buggers will not leave you alone !
Good luck !