HI
I used Wiljam for a resit, costs about a fiver a month, and in my p of f resit, i had seen all the questions before on Wiljam. I didnt register at bristol cos of the cost, about 50 quid i think. If you want a comparison i would say you get what you pay for.
All you get with with wiljam is access to an atpl questionbank, but woulld say having flicked through the other subjects the question bank covergage was excellent, but so is bristols. Wiljams questions are all in PDF format.
I have been told though, that with the fee to bristol, you also get access to a forum where you can post questions answers etc, so in that respect bristol is much better, because with wiljam your on your own. (but is is only a fiver or six quid a month)
I did read after i posted on another thread though, that WILJAM is no longer running, but i dont know. If if is still running though and you intend to use for a few months, i would pay the extra to bristol just to get access to the forum because you wont save that much going to wiljam.