I realise the last post on this topic was a while back, but I am modelling Aberdeen in 4mm, late 50's/early 60's. There existed a 4 coach ex LMS TPO set which formed part of the West Coast Postal, and which ran into the 1980's, albeit with Mk1 TPO vehicles by then.
Is there anywhere I can source ex LMS 4mm TPO coaches, or coach kits? Can anyone identify the vehicle types from the pic below? I suspect some were sorting vehicles and others were fitted with nets etc for pick up at speed.