QUOTE I got that site but there are no interior photos.... Now I know why Ian Kirk did not provide interiors with these models, they simply didn't know what they were like.
Follow the link from the NNR rolling stock page to the M&GNJRS page, there's a slideshow at the bottom including an interior shot. And I suspect Mr Kirk actually travelled on them (or something very similar), but many coach kits in those days didn't include interiors.
http://www.mandgn.co.uk/page.php?pid=19 Alternatively this is the first hit for "quad-art interior" on google images -
https://flic.kr/p/14957468847
QUOTE I have just acquired a Hornby R449 LNER Clerestory Brake Coach with no interior. Would anyone know where I can get an interior seating kit for this model please?
That's another non-corridor, cut some partitions from 30thou styrene sheet, make a floor from more 30thou, cut some Ratio seats to length and fit them either side of the partitions. Paint all the woodwork darkish brown and the seats any dowdy shade of dark red/blue/grey/brown you like, you won't see most of it through the windows anyway in other than strong light.
The Peco kits are fold-up card kits designed to fit the old Kitmaster kits but they can be made to fit any Mk1 with a bit of effort. They represent 1950s corridor coaches, not older non-corridor stock. The Comet kits include etched compartment doors or seat ends (depending on coach type) but the partitions etc have to be cut from styrene sheet.