Thanks as always everyone!
Some more work over the last week on the upper decking. The front section was made by bending and heating sheet plastic over a balsa form. It's not perfect but it will do. The rear decking was also done with 0.05" card, scored to represent the stringers on the upper decking, then bent and glued around the curved bulkhead behind the cockpit. I still need to re-work a number of areas around the cockpit but you get the idea. I also recently got hold of the CSM RAF4a engine (thanks Edgar!) which is very very nice. I've positioned the crank case for effect.
These parts took a few hours to make (the upper decking took a couple of goes to work out how to get it together) and they turned out ok, but certainly far from great. Good enough to move ahead with though. These will take some clean up to smooth out the transitions and seams once the fuselage is all glued together. I don't see this as being too major an issue, especially as I can hide some of the seams with the fuselage stitching.
Cheers
BC