It is a Hornby R461 Straight platform with subway stairs. Here I have a platform for sale.
HORNBY R 461 Platform Straight With Subway
HORNBY R 461 Platform Straight With Subway Stairs
Hornby R.461 BR Mk1 Sleeper Coach
HORNBY R.500 PLATFORM WAITING ROOM RED OO GUAGE 'HOGSMEADE' USED UNBOXED
Hornby ~ R.514 Platform Canopy , REPLACEMENT SKYLIGHTS FOR 2 CANOPIES 3D PRINTS
