Could it be the Arcs AKA Arcadium Ballroom you're talking about? Can't remember a backroom, though.
The Arcadium Ballroom, Accrington on Manchesterbeat - the group and music scene of Manchester in the '60s
Champion Jack, although originally from New Orleans, lived in Halifax in the 60's, after marrying an English woman and appeared at lots of venues around the country. Saw him give a brilliant performance at the Jazz Club, circa '68/'69.