Hornby made a rather bizarre selection of vehicles for their five Gresley coaches. The buffet car was a very sensible choice, but they could really have done with end vestibule side corridor third brake, first and third in place of the side door vehicles as these lasted longer in BR traffic; and the ubiquitous and widely travelled full brake instead of an uncommon sleeper. (Bachmann in their range of Thompsons did include a full brake - one of the rarest LNER full brakes, about as common as Hornby's sleeper!) Perhaps no one at Hornby realised how long the Gresley full brakes lasted in traffic all over the BR network.
The simplest solution are the Ian Kirk kits now available from Coopercraft. These come in 61'6" and 52'6"corridor and 51' non-corridor types, and also from Coopercraft the Mailcoach Thompson Matchboarded full brake. You can also graft a Gresley roof onto the Bachmann Thompson full brake, to produce a passable Gresley steel panelled 61'6" full brake. Rather than bother with the floppy kit bogies buy Bachmann's 'Thompson' (actually Gresley) pattern bogies.