Personally I've found Oxford excellent. Yes, they have lots of exam feedback, but more importantly, the quality of ground instruction is very good.
That said, feedback questions are all well and good, but a thorough understanding of all the subject matter is more important. If you into a JAR exam thinking you know what's going to come up because you've seen the latest feedback, you'd better be careful! Think they add to the question bank fairly regularly in some subject areas, so it's constantly changing.