In my original post I didn't think to show the bike the way I got it, as that build didn't seem .. um .. very original. But now that I see the Halford's some parts may have been original after all. It came with the same Shimano 60/600 derailer set:




The hubs are Shimano HF with straight QR blades and "RR" date codes. Pre-1976?



Oh, and there's serial number on the BB shell, which has been widened from 68 mm to 72 mm, presumably to host an Italian-sized spindle: