That one looks very much like a Branchlines kit. Can't be Roxey as their only six wheeled passenger carriage is the Stroudley four compartment first, and it would have had oil lamps as well. It could be a Microrail/Gibson/David Geen full third, but if the others you've got are a different type, then Branchlines is your man, as Microrail only produced the one type, with a couple of NPCC to boot.