You simply sign-up to the questionbank for as long as you need it. I've just paid £50 for three months access.
Looking at my overal spend, going with CATS online, buying second hand BGS notes on Ebay and subscribing for questionbanks (ATPL online and AVIATIONEXAM.com) I'll have spent around £1500 by the end of the course (not including exam fees of course).
That still compares pretty favourably with BGS which I understand costs over £2000 - and also has a bit less flexibility than CATS in terms of subject order/brush-ups.
Last edited by taxistaxing; 8th October 2012 at 13:15.