Superb work, I'm tempted to buy one or two!
Have you though about an earlier Speno Rail grinder as seen in this pic? http://www.philt.org.uk/keyword/taunton/1/1406453490_N3xbNjj#!i=1406453490&k=N3xbNjj
It looks easier to modelm, and ran around in the 1980s so I would definitely need one for my layout!! Interestingly enough, they were crewed by Italians, who lived and worked on the vehicle and where guided round the Network by a BR conductor!