Peter, Roger and Chris, I have the track plan book but have been out for the evening so only just have had the chance to get back. For Roger and Chris, the book has little more info except it colour codes the track pieces and tells you how many of each piece is needed. It tells you nothing about power connections, IRJs needed or what makes up the RLs.
Chris, now you can see an RLM is needed, in fact while I've yet to get my head around that area to be definitive about exactly how to view the RLs and their isolated sections, I'm pretty sure two will be needed for flexibility in operating the RH loops.
Peter, Roger has used the word adventurous. I'll go a little further and say that before I attempted to build this, I would be doing some testing on functionality. The things I'd be checking would be first the inclines as you'll find the recommendations on here are for a much lesser gradient than in this layout using standard Hornby inclined pier spacings. Then I'd be making sure the curved points work without derailing locos and carriages as configured, then also derailing on the standard points.
Then in Chris's diagrams, I personally see little point in splitting the DCC control into track and accessories. I'd keep with the simpler writing. And yes use the Elite and put the eLink in the bottom drawer (next to the Select if you have one of those).
This layout does not need a booster as such, nowhere near big enough for that. However, as it needs two RLMs, the booster can be used as the second one as it does polarity switching just like and RLM.
I'll think more on the RLs and come back with ideas tomorrow if no one else does. You will only need IRJs for the idol;aged sections in those, not elsewhere.