Hi,
I would be carefull about cancelling the ppi as it may not make that much difference.
The policy you have bought is a single premium policy which is added on to your loan and also pay interest on too.
The new ruling is in relation to "nil refund policies", meaning that all firms must over "partial refunds"
You will find that your refund will not be a pro rata refund but prbably about 10% of the premium. Your repayments will also only go down by a few £ as you will still be paying the other 90% of the ppi policy and the interest on it.