Thanks, Juvela! It is an Alatet? Then this will be my first Alatet, which, I think, was top-of-the-line. It's interesting what you said about Brampton and T.D.C. The both produced the Continental model, too (the one on my Grubb is Brampton, probably original)
I think Tom Cross called his the J model, as well. I think the nicer headset on this bike and the Legere with windows (#45) points to an upgrade from the Grubb, which would be consistent with the way Holdsworth marketed the Claud Butlers. We still see the stamped dropouts and fork crown, though, so it would be the least-expensive C.B.
It will also be getting a set of GB Sport calipers, Grande Bretagne bars and Arret levers.