I've found sound time today and have finally started to lay some new track. I had to cut the rear platform line back somewhat to get an undamaged bit to join new track to. When I originally ripped up the old loop points and part of the loop I pulled the rail out of the chairs but all is now nicely connected up. The new platform lines and the goods loop are nailed down and cut to length, I need to make holes in the baseboard for the point motors, but before I attach these I will wire them up to make life easier at the control panel end.
One up shot of laying the track this far is that I can now work out where the river bridge needs to be and build appropriate abutments and then make the river bed before I install the bridge and make life difficult for myself as usual.