Don't know if this has already been posted, but I've noticed since signing up to a recent lovefilm trial that you now have to phone to cancel and can't just do it after 10pm like the old days. However, if you use the link below you can cancel anytime online, I assume you just need to be logged into lovefilm to cancel:
Hope it helps those taking advantage of cashback/free trials!
MUST BE LOGGED IN.
THEN GO TO