Comparison sites can be very helpful to get a short list. Beware very cheap prices as the policy offered might have very high excesses and might not offer pillion cover or third party cover to ride a mate's bike. Check the "out of garage at home" clause very carefully. Some are worded very harshly.
Read this, it mostly applies to bikes as well
https://www.moneysavingexpert.com/insurance/car-insurance/ - especially follow the advice about not leaving insurance to the last week. You will pay extra compared to applying 3 or 4 weeks early.
Personally, I don't really care who sells the policy, I look to see who underwrites it. If the broker turns out to be rubbish you can always go direct to the actual insurer in the event of a claim.
I have 2 bikes. I have looked at a multi-bike policy but for me, two separate policies on full NCB works out cheaper. One policy is from Devitt, the other from C Nash Select. One is underwritten by Axa, the other Aviva.
I looked for prices via the Moneysupermarket website then had a look to see if the same broker was offering a cashback at Quidco or Topcashback. This brought my premiums down a bit more and I have had the cashback into my bank. I'll be repeating the process next month as my policies are due on separate dates in June.
I have a car, 2 bikes and a house to insure, so I have become quite good at playing this game. Fortunately no claims since 2005 on the house policy after a water leak. That involved binning the useless broker and going direct to the excellent underwriter. Groupama in that case, who used to own Carole Nash when they were a half decent broker. I believe they are not so good under the latest owner.
Prices paid: R1200RS £110 with Devitt/Aviva; XR £88 with CN/Axa. RS is higher due to more miles per year as it would normally be used for commuting. Prices include the cashback: £21 from
https://www.quidco.com/compare/motorbike-insurance/ for the Devitt policy and £26.50 from
https://www.topcashback.co.uk/category/bike-insurance/ for the CN policy