Don't cancel the policy Chris, that is letting them off the hook, let it run its course if you can't suspend it, you never know.
Think about it this way, if you had paid for the policy for the year in one payment for example £600 (£50 a month)
If you have the mini stolen after the month you can go back to them and say oh i want £550 back as im not going to use the car anymore...
Its like buying something on finance, if you was to sell it you would still have to pay the rest off...