3d wagon works
Arch Laser
ATD Models
BBD Ltd
Bowater Models
Buggleskelly: now with a new wagon for pre-order!
Bunter’s Yard
Copper Mine Miniatures
DAPR3d
DCC Concepts
Hornby
Heljan
In the GreenWood Laser
Jsets0
Luk-Greav - eBay seller 
LGModelRailwayStore - small 3d printed manufacturer but growing!
Lincoln Locos
MacTrains eBay seller link, for direct sales click here
Man with Trains
Modelu
Moor View
MS Models
Noch
Osborns
Oxford Diecast
Peco
Prieser
Railtec
RailwayScenics
Replitek
Revolution
Rusty Rails Modelling
Scale Model Scenery
Scale-O-Rail
Silver Tay
That Model Railway Guy: awesome drystone walling - when it's in stock!
Three Peaks
Tillig
TramFabriek
True to scale
TT Scenics
Westhill Wagon World
Willington Dene
York Model Rail