ATPL Theory
Its was about 4 years ago I did ATPLs. A lot may have changed since then, but heres my angle.
Everyone is going have their favourites on this one. People learn in different ways and for the best transfer of learning to take place, you need to find the person that suits you.
I studied the majority of the course with Gavin Secombes correspondance files. Whilst I found them neatly presented, I couldnt help but feel that a couple of topics strayed a bit far from what you need to know in the exam. Gavin is a very knowledgable person and teaches you well in excess of the subject matter. You will find Gavin to be a very pleasant, well-intentioned chap.
I passed Met, Performance, HUF, and Air Law with Gavins coorespondance system.
I was running out of time (3 years) to do the last two (getting caught up in working for a living as a GA pilot whos boss wouldnt me have time off for the exams). I needed to get through the material quickly and concisely (and pass!). I went and saw Nathan Higgins in Maroochy who came to my rescue.
I parked my ass in the first row and opened my ears and asked lots of questions. Made it through first time with 94% in flight planning and 92% in AGK.
Nathan Higgins is certainly very knowledgeable in the same respect as Gavin Secombe. I certainly did feel that Nathan was much more energetic and had his finger on the pulse.
If Gavin Secombe ran a sit in class then that would also be of great value.
Either way - Just get into it. The sooner you start, the quicker the headaches (and that heavy weight on your back) start to abate!