There's definitely a time limit, but if you had the payments set up via direct debit then usually having your bank delete that DD from your account is enough to stop them taking money (i'm not condoning this in a situation where you actually have a bill to pay). However companies have been known to illegally re-set DDs back up on someone's account.

Follow this link to the full copy of the Data Protection Act, which should give you all the details you need:

http://www.ico.gov.uk/upload/documents/library/data_protection/practical_application/subject_access_-_guide_for_data_subjects.pdf