Hi all
There are a number of detail differences between the loco-hauled and HST versions besides the presence or absence of buffers. The main differences are in window layout, especially on the kitchen side, but as far as we know Dapol have already decided to only produce the RFM, which is a loco-hauled Mk3a vehicle.
So, accepting that the window layout will be wrong for the HST versions, the other main difference between HST and loco-hauled Mk 3 catering vehicles is that the application of Blue-Grey livery was different on HSTs. The main differences are: a narrower rail grey band around the windows on hst trailers; broader red (catering) or yellow (first class) cantrail band on HST trailers than on loco hauled stock; white lining between grey and blue areas curves round onto end doors and runs vertically, parallel to gangway on loco-hauled but is cut off at the gangway end of the door on HST stock (difficult to explain - see photo links below). A loco-hauled blue-grey Mk3a in an HST will stick out as non-matching because of these livery differences.
There were also differences in branding depending on the vehicle in question:
Mk 3a RUB (loco hauled, 3 large saloon windows per side, number range 100xx): "Restaurant-Buffet"
Mk 3a RFM (loco hauled, 4 large saloon windows, number range 102xx), as repainted by Cargo-D: "Restaurant-Buffet" or "InterCity Restaurant-Buffet"
Mk 3 TRSB (HST buffet, 4 large saloon windows, number range 400xx, later 404xx) originally "Buffet", later, from around 1979, "Buffet-Bar 125"
Mk 3 TRUK (HST kitchen, 4 large saloon windows, 405xx) originally "Restaurant", later "Restaurant 125" from around 1979
Mk 3 TRUB/TRFB (HST kitchen buffet, 3 large saloon windows, 403xx and 407xx) "Restaurant-Buffet 125"
Here are some pictures which show the differences:
Mk 3 TRUK in an HST, kitchen side: http://www.flickr.com/photos/blue-diesels/3900183338/
Mk 3a RFM kitchen side (loco hauled): http://www.flickr.com/photos/45726467@N02/6448899637/
Mk 3 HST (left) and Mk 3a loco hauled (right) vehicle coupled whilst on test, showing differing width of rail grey bands: http://www.traintesting.com/images/Mk3-coach-SIG_bogie.jpg
Given these differences in livery application, it would be reasonable for Dapol to produce two Blue-Grey buffets, one for the HST and one for loco hauled rakes. Perhaps Dave could give us some clarification?
Incidentally, the MK 3a RFM vehicles never wore blue-grey livery when operated by BR as the type didn't exist until the mid 1980s - the original loco hauled Mk3a was the RUB, which had only three large saloon windows. All of these RUB, plus some HST TRUK and Mk 3a FO, were converted to RFM with four large saloon windows from around 1986, outshopped in Executive or INTERCITY livery. Only in the last few years have a few RFM been outshopped in blue-grey, by Cargo-D, and subsequently used by Wrexham and Shropshire.
Hope this helps.
Tom