As you have spoken to O2 this may not apply to you but, the Terms and Conditions for O2 Home Broadband and O2 Home Phone Services do state the following; which I think is meant for people still in contract and not for those out of contract I presume!
http://www.o2.co.uk/termsandconditions/broadband/hom...
8.4 After the Cooling Off Period, you may terminate your contract:
a) for our 12 month packages, by sending us seven (7) days� notice by email, fax, in writing or by calling us.
You can also give us notice by ordering service with a new supplier, but please make sure that we get the right amount of notice, as set out above. The details can be found on the Contact Us page of the Website. The postal address is: Customer Service, PO Box 202, Houghton Regis, LU6 9AG. You must pay all Charges incurred up to and during the seven (7) days (as applicable);
Edited bold
Edited by deleted (Fri 18-Jan-13 13:46:06)