Second comment ... lots of these Brit frames were sold either mail order, or through American LBS's as bare frames, so you see a lot of variability in how they're built up. Standard for a Jackson or Woodrup (or Witcomb or Claud Butler or Holdsworth or ...) in the early '70's was all-Campy NR; about 1980 you start to see Shimano, particularly Dura-Ace, and Suntour, either Cyclone or Superbe. The downscale parts on this one suggest to me that you're seeing stuff that was put on there after the original build.

And +1 on some stuff which unworthy1 said; Doug Fattic is one of the guys who posts a lot on bikelist.org, so if you post a question about your frame there, you might get a response from him, as well as some others who have a lot of firsthand knowledge about the marque.