Stuart,
your call, of course, but I would suggest that getting a few mates round and running some trains might give you the motivation to continue.
my ambition is a model, something like yours but based in Wales, for which I have much of the required stock, a trackplan, and the locoshed built as a module to attach to the layout. What I do not have (yet) is the extension in which to build it.
My experience of larger layouts is that the builder funds it and does much of the work, but it is the crew who make it live. Having got so far, it seems a great shame to rip it up and start again. Four block instruments and a few pals…