It only ever had the Red Backed plates in preservation. As modelled by Hornby complete with the LA branding under the drivers window which is only correct for preservation
The NRM dont have a set (they have the Sir Edward Elgar GWR Castle steam ones though) - Ive seen a genuine set (name,number, BR arrows and GWR Crest) owned by a member of a Class 50 preservation group, among the last things to be cast at BREL Swindon too, and cast brass so very heavy
As regards them selling or not, who knows, most of the Kernow Exclusive models can still be got from them, 512 editions. Personally I feel 50 or less is a true Limited number, but Hornby wouldnt make them in that few numbers without a big surcharge