I found out yesterday that our Pets at Home are now selling beef ribs, duck and turkey necks and beef oesophagus alongside their frozen meat and Natures Menu stuff. Apparently some other stores also have heart, kidney and liver.
No.1 son works there and because we feed raw he's quite the zealot. He is really pleased to have a decent range of raw that he can recommend to people. It doesn't seem particularly cheap but useful as backup when the local market doesn't have much.