Hornby Dublo did not make many BR (SR) Mk1 Green coaches and as a result they are
fairly hard to find and on the expensive side. For a M&B expect to pay around £70 and for a good unboxed up to £40. I have three of them unboxed and paid around £25 each, all bought at train fairs.
I also have a couple of Kitmaster green MK1 but neither were a brake so the short rake was a little odd. I added a Trix Buffet Car version which had been fitted with HD bogies and that was the state of play.
Then I saw on ebay some Trix BR (SR) green coaches, bid for two brake composites and one both of them for £4.99 each + postage. They run without any problems on their Trix bogies so I am unsure why the Buffet Car was fitted with HD ones. The net result is that this carriage rides a little higher that the originals.
So if you are a runner and want some BR (SR) green carriages keep a look out for the Trix ones. They are all plastic, rather than the HD ones with their tinplate sides but look good and run well. They also do the buffet car which was never available from HD. Coopertrains have produced new versions but you would have to pay £140 for the buffet car and £125 for the brake. They are lovely models but for a runner?