Most of all, do not make the mistake of getting a JAA PPL, as you will loose it upon gaining the CPL and be spending more than necessary.
To clarify I think what you mean is all you need is an ICAO PPL before starting your ATPL theory and then the ME/CPL/IR which is of course true. Plus your radio licence which you can do when you are back in the UK if you intend to do the CPL/IR flying or work in the UK. If not then don't bother with that either. An FAA PPL is all you need to get you going which should save you some bucks.
Anyway its all in LASORS and can be downloaded for free from the CAA website and is a must read when starting out to see what you are in for. Particularly the bits about time limits so that you don't lose credits or ratings along the way whilst robbing peter to pay paul.