Thanks BSA-Bill and John,
After looking at your links I think I now know where George Prew was coming from. I asked him for a genuine BSA clamp and the ones in the links are not. Obviously suppliers are using the BSA part number for an alternative.
This came to light after phoning Simon from Barleycorn Eng. We had quite a long chat about him trying to replicate the original and having little success due to its complexity. What he described to me was nothing as simple as the ones shown. He did say that he would have another go at making a replica but I'm not too sure how successful thats going to be so in the meantime I will get one from Tri-Cor or Burton.
Col.