I just renewed mine. My policy was with Hastings. They quoted me £326 to renew. I didn't use a comparison site, but went on to Bennetts as I like the fact that they support British Superbikes. Their price was about £220 which was very attractive. But then you find that they have left off loads of stuff which they offer as "extras" as you head to the checkout. A bit disingenuous in my book, as well as very annoying. When I put on the same features I had on my Hastings policy the Bennetts one went up to about £300. I rang Hastings and they immediately dropped their price to £226 without me really trying. So, try pinging your existing insurer first and say you'll leave unless they can give you their best price.
Principal Insurance as broker , Insurance thru Aviva 465 quid all in Pretty good considering I called them the day I passed my test and told them I wanted to insure a 1200 Multistrada ( I had overseas riding experience , but zero in UK ) so I thought it was a very good price. and guy I dealt with was very helpful, and did his best getting me a good price by phoning various insurance companies direct. Worth a try