Lovely bike. I often chat with Mark Swinnertons at Cannock Chase Cycle Centre about the 'old' days. They did have a frame builder at Swinnertons back in the day and yes they also used Longstaff.
Mark is a really lovely guy - I'd give him a ring to know anything about the Swinerton history. He's Paul's older brother btw
Would anyone recognise the lug work on this swinnerton, I don't think its a Longstaff built frame as the seat stays are not his style but, was maybe thinking Rourke due to the wrap over seat stays rather than Mercian ?