Have managed to arrive at something not unlike a consensus - Not sure this isn't a bit complicated for a beginner though. Tried the Atlas RTS software but lacked the patience to work out what bit of track corrects for a turnout so ended up using their bits cut and pasted to get something about right (then allowed some extra for errors). Still a bit rough but shows the basic plan.
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Baseboard materials have arrived, trestles under construction.
Regards
Mike