Here's a bit of an update on this bike to try and spurr on the build
I found a 1990 buyers guide with a spec for it, see attachment below, this is great as it confirmed everything I remembered about the original spec, apart from the rims where were Rigida (a bit annoying since I had already tracked down a set of NOS M6CDs and had them built up onto Suntour XCD hubs) but they meet the spec well enough (anodised, wide and heavy that is!).
The frame is in worse condition than I thought so its off to Argos, once the decal god Gil-m has sorted me a set of repro decals, (wil get you the info soon Gil!). Had a spot of luck here as I managed to get some pics of a 'Montana' the 501 magnum version from the same year so decal sizing/font/location etc was made much easier.
Most of the parts are gathered, will post some pics over the next few days - its been pretty hard to track down a full XCD groupo but its done now
Just need an 'Isca Gel' saddle now - anyone got one?