Following on from my last post, I've found a few answers to my questions regarding constructing the track away from the layout.
From various responses to a posting I put on the newsgroup, it seems that the recommended method is to temporarily sellotape the paper templates to a flat surface (a piece of chipboard left over from my butchering of the bookshelves should do fine!), build the track on this, then when complete, carry the entire formation (plus temporary wooden base) to the layout baseboard, lift (or slide) templates+track into place and install.
This sounds ok. I'm not sure about fitting wire droppers to tiebars for point motors to attach to - where would these go during construction? But I'll cross that bridge when I come to it.
I haven't actually bought the track components yet, but I have been refining my templating skills in Templot - I've finally begun to get the hang of using it. It's still fairly slow work, but then I suppose designing something of this complexity is never going to be just a case of a couple of clicks!
To begin with I was just creating individual turnout templates. But now I've begun to put it all together into one big layout design. the advantage of this is that I can see exactly where everything will go and how it will fit into the space whereas up until now I've been using a fair bit of guesswork and approximation. One thing I have noticed is that using scale turnouts increases the length of any track formations at least slightly from what I was working to before. This is not a problem though as there is still adequate space for what I want.
I've reduced the number of 'Y' turnouts to 1 now - the tournout in the goods yard was going to be a 'Y' but working in Templot, I found that a standard LH turnout is better, moving the goods shed road a little further from the platform loop which I think will give the illusion of space more than if I had three tracks running parallel to each other. The only thing to watch out for is to make sure theere is adequate space between the two goods yard sidings.