I finally tracked down some suitable square shank buffers for the 2-Bil. They are Slaters GWR coach buffers, and are sprung. Not cheap but very nice.

This has spurred me in to finishing this unit. The inner ends have been detailed with various bits of wire and plastic (not the best photo as the roofs aren't attached and the toilet fillers aren't properly attached yet),

The worst bit was doing the toilet filler pipes - I hate bending bits of wire in umpteen different directions. Anyway, it's now ready for a spot of green paint.