Rob,
I can give you the little bit of information I have on 41734.
It spent its whole working life at Newton Abbot and was fitted with pipes for both vacuum (for brake release) and steam (for carriage heating), both of which hung down below the headstock. This particular 'Chariot' was primarily used on the carriage siding shunt duty (hence the pipes) paired with 2021, 57xx, 74xx, 94xx and from 1959 onwards 400hp diesel shunters. One account questions whether the steam heat was ever used on stock in the sidings, but it seems odd to have gone to the trouble of so fitting the M3 truck if it was not to be used. Another snippet I have is that the original angled lamp irons were replaced with the sloping variant on the toolbox (as per the Bachmann model) in May 1936. Additional irons were fitted to the buffer beam in Feb 1950.
There is a photo of it attached to a diesel shunter in GWRJ 26, obviously in a guise too late for your period.
Hope this is of interest.
Regards,
Andy.