I'd see if you can find an arable farmer to talk to for they would be best placed to tell you if they grow them in the UK .
I have a feint memory from 30 odd years ago of one of my farmer pals...aka Barry , saying that he was going to try it for cattle feed but that could have also meant him using the stalks as well as the actual bean & pod.
We've moved to several new homes since then , so I don't have contact with him on a day-to-day basis to check it out .