Thanks to all that have given advice, and Chris for looking at my layout plan. Here's my layout so far:
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I've still a few decisions to make as yet, and I am fitting some new express points between the up/down main lines. There should be a bit more rolling stock in the next few days too, I got some teak Flying Scotsman carriages off eBay (new ones), and a small collection of goods wagons.
It's my intention to motorise the points before I fix down and landscape too, and I already have a set of switches. My plan is to build a track plan on a board with the switches mounted in the positions for the points.
Apart from needing a few more points, and possibly some more straights, purchasing of track and stock is at a point I can get on with most of the work now. The initial expenditure is out of the way, and I can now add to the layout as budget allows.
All the best.