I am the hot pursuit John Spurr,now living in France and riding my bike on the pyrenees. Its great to know people still remember
I heard you'd moved to France - Totnes is not the same without you and the shop in the centre.
As to the bike, I remember Guy was building these around the time I bought a similar spec Sonic from Helmut Berns in London. Guy was renowned as a very hard rider - can't remember a group ride when he didn't break something or puncture at least twice. Suspect that, as a consequence, his frames should be pretty durable.
I also remember lending him, with some trepidation, my Campag front wheel at Newnham once; was very surprised when it came back in one piece!