Hi mate. Sorry to hear that the insurance guys are up to their usual games. As suggested above, I would definitely try what others have said, ie try a few comparison websites. Give "thebikeinsurer" a go as well. Again, it might also be worth waiting till you're up for renewal and going for a different company.

Here's a curveball: have you thought of getting a second bike purely for commuting and getting business cover on that? Maybe get some quotations on something like an ER5 or similar. You never know, the total cost might be cheaper than what you've been quoted so far.