Well after a lot of knuckle scraping and fannying about with brake options oh and a change of mind regarding saddles, it's finished...
After the first (& successful) test run I decided the Selle Royal Pullmans weren't quite as comfy as I'd remembered so swapped them out for a pair of Specialized Lambda flags I had put away for a Cape Wrath build, these were the original catalogue spec and comfy as well.
So is it a RetroMod? I'm not so sure... The wheels are new builds and the stoker operated disc "drag" brake, so are the front suspension forks. The dampened seat posts are circa late 90's, the Bluemels are new but based on a design thats at least 50 years old.. the grip shifts are circa mid 90's.
Everything else (excluding consumables) BB shells & axles, cranksets, pedals, brakes, brake levers, rear mech, front mech, saddles, stems, handlebars and last but not least the rear rack are 1987-1990. So for a bike from 1987 that was likely to have been built up in 1990 its hardly super modern.