You will be charged what is known as short term rates for cancelling your policy early (outside of the 14 day cooling off period - in this period you will only be charged for the amount of days you have actually been on cover + an admin fee for all the paperwork and documentation etc, circa £20)). For short term rates I would expect them to charge at least 3 months cover if you cancel in the first month + a cancellation fee ( this can be quite high (circa £50) but is all in the terms and conditions you signed up to.

Hopes this helps you understand the charges even if it doesn't make you happy about them.