In the latest GOG Gazette is an advert headed 'Quainton Road Models' - a fondly remembered concern that appears to be in new hands.
Apparently they are working on a kit for a GC six-wheeled fish van. This has to be diagram 49, which looks rather like a 6 wheel coach gone wrong. They were built by Metro Amalgamated C&W at Ashburys in 1900. There were only four on the whole line (No. 28591-28594) so even if you're modelling Grimsby Docks I can't think you'll need more than one kit. Interesting choice of prototype!
I've never seen a photo of one of these, and how they were lettered is anyone's guess. Indeed, I wouldn't even like to swear what colour they would be. Probably brown first, grey later.
Why the GC chose to built 4-off of this non-standard type is a mystery to me, but I suppose it adds variety to a fish train or passenger train tail traffic...