Cheapest ain't sometimes the best. Some will sting you 25 or 30 quid a time if you make slight policy changes during the year.
Consider if you are going to make any changes in a year

Most of them want totally standard bikes and not many of us ride them. Get involved in a expensive serious accident where you have to pay other people and they may have a loop hole to not pay.

Beware of "free" breakdown cover. The "free" can be very restrictive. Some will only take you to nearest garage and others have a max claim of a few hundred quid a time.
£300 is can sometimes only be worth about 50 miles in breakdown recovery