Diplome, Wiggy,
At the risk of sounding a bit like an anorak, Chris Darke, who was the Gen Sec of Balpa from about 1992 did know some of the SW crowd, not through personal allegiance, but through his previous role at ASTMS (OK, later called MSF).
So Balpa are as capable as bassa at "being associated with" Socialist Worker.
They used to meet at a charming Westminster venue, which no longer exists, called the Victoria Club.
"Creative External Redeployment", anyone?