What a mistake. They have their own rules and don't make it clear what they are when applying for insurance. They make it clear enough after you've signed up though, and guess what? There's no get-out option, so you're completely screwed.
My son's £500 (the first review said £5,000 - it wasn't) Corsa van was bad enough to start with at £2,000 for the year, but went up to over £5,000 in the first month, because 'their rules' state they don't accept certain types of no claims discount evidence. And they never chased for that evidence, preferring to advise that as it hadn't been provided they were increasing the premium to £5,056.00. When it was provided, they then advised that it wasn't suitable, so we provided further evidence; still not suitable. We withheld payments to get the policy cancelled and now they're threatening all sorts, including sending debt recovery agents (heavies) around to knock on my door. They can't honestly expect me to pay well over £2,000 cancellation fee, surely.
We paid the insurance for the period the cover was live at the original quoted rate and not a penny more. There's no chance of them getting anything else.