I just cancelled mine on monday. No charge and they were very helpfull. My next instalment was due today and they said it would not be taken but if it was to let them know and they woudl immediately refund it.
hahahaha, pet pla are very good at not cancelling your policy. i sold one horse that was insured with them in june, and only in december was i still to find i was still being charged his insurance! And getting the money back off them was a nightmare! if your cancelling with them make sure you get it in writing!