Dapol suburbans query

I've just bought a pair of Dapol suburban coach body bare shells for peanuts
on eBay, as new surplus stock (ModelTrains4U: highly recommended trader). I
blithely assumed that they were either a GW design or the BR Mk1
non-corridors.
On closer examination, though, they're not. They appear to be a
composite of some sort - the middle four compartments are a bit wider spaced
suggesting they're firsts, with seconds at each end and a pair of lavatory
windows towards the centre - and besides they have ovalled ventilator panels
above each door which makes them an older style altogether.
So: what are they? Not very good at identifying coaching stock if it's
not in Jim Russell's GWR book, or obviously Gresley-panelled or BR-built
stock! Someone say it's LMS so I can stick an appropriate tank on the front
for my Brum/Worcestershire-inspired layout.
Tony Clarke