After much thought and deliberation, lots of questions, lots of reading, lots of surfing... I have decided on a track 'system':
I will use C&L flexi track for the plain track, and build my own pointwork using C&L components and custom templates designed using Templot (I've been playing about with this software for a few weeks and despite its complexity and general non-user-friendliness, it does enable me to create pretty much anything I want).
The advantage of using Templot over the C&L produced templates is that C&L's 00 gauge point templates have too close a sleeper spacing compared to the prototype and even, as far as I can ascertain, compared to their plain/flexi track. Also, with Templot I can also produce 'Y' points, combinations of points, as well as adjusting timbering, etc.
But if it hasn't already taken me long enough to decide on a track system, I now need to decide what I'm going to build it on! Building it in situ on the baseboards is out of the question - I need to be able to build, ballast, paint and weather it in sections away from the layout and only then install it all in situ.
This means I need to decide what to construct it on and how this will then be transferred to the layout, and whether I need some sort of extra underlay on the basebaords, or if the base I construct the track on will be the underlay....