Macky,
I would honestly recommend that you get the Jeppesen JAR ATPL / OATS manually from one of the pilot suppliers and read it thoroughly.
I found it extremely useful, and then did a brush up course with OATS and got all their feedback. Needless to say it was spot on and I got it first time.
I do think that my grounding by our Instruments instructor when I was at SFT (Steve Williams) was excellent. Unfortunately they're not around anymore, so (not trying to plug them, I have nothing to do with them, but..) get yourself off to oats, it worked for me!