Some progress over the past few days since the drop in temperature has made the modelling room more habitable.
The support bracket for the expansion link has been made and is seen here loosely placed in position on the motion bracket. It's dimensionally right but only representative in detail.
The inside cylinder has also been fabricated, complete with the unusually long rear valve chest. Where possible, I'm using commercially available bit and spare parts, so the valve spindle guides and cylinder covers are from the Comet standard LMS/BR etch. Not strictly prototypical and some spare, unwanted holes, but it saves scratch building. The front and back cylinder relief valves are just the mounting tube at present and there's the drain cocks to do.
Here is the cylinder assembly.
And here, loosely placed in position on the RH mainframe.
Slide bars and then valve gear rods next, I suppose.
Dave.