Sheesh there is no way I would put modern parts on a frame like that. That crank is awesome,,, seems a horrible end for such a proud frame to have new parts on it, unless they are really tastefully hidden, like bearings in the BB.

You can find adaptor plates for Campy- I have a Valentino on my older Bianchi set up that way. Shifts very nice BTW.

If you go with SA put an AW on there- you'll be able to fit it without bastardizing the frame anymore. Some of the charm of the older British stuff is finding how well it actually works when set up right. GB brakes are wonderful- I am a big fan. I like the Coureur 66 centerpulls the best- and they are the best of all the vintage centerpulls by a country mile. I would see if I could find a Huret Svelto to act as a rear chain tensioner and put a Huret derailleur on the front. With the AW hub that would give you a nice range, and a good excuse to use that beautiful crank.