24 minutes ago, Downer said:

Does anyone know the composition of BR’s ‘The Caledonian’ rake, and whether it will be possible to reproduce it with BR-liveried versions of the forthcoming Coronation stock?

The Caledonian varied over time. The only Coronation Scot carriage of use will be the kitchen car. In the early days of The Caledonian, the brake first was a 'porthole' so already available from Bachmann. Apart from the kitchen car, the remainder were BR Standard (Mark 1). Two open firsts (available from Hornby), originally three 48-seat open seconds (also Hornby) and a brake second corridor (Hornby or Bachmann). Some of the open seconds became 64 seat or side corridor ones if I recall correctly, and the BFK became a Mark 1 (not available RTR). Later, the kitchen car became Mark 1 too although if I recall correctly towards the end of the train's life, it had an RKB.