These coaches were the last GWR-style auto trailers to be built. They used GWR diagram numbers, designs and control equipment but were built entirely under BR auspices. The body shell was identical for all four diagrams, the differences being in the layout of the interior.
They were in service on many of the ex-GWR branch lines either working as a single coach or with other auto trailers and intermediate trailer coaches. Several worked the Clevedon branch from new until the end of steam working. They could also be seen on the Abingdon, Marlow, and Calne Branches. They worked on the Chalford-Gloucester, Cardiff-Pontypridd, Leominster-Ludlow, Ledbury Junction-Worcester and Exe Valley routes and have been seen as far apart as Paddington and Wolverhampton. W220 and W221, as Thrush and Wren, worked the Ealing-Greenford route.