Thanks for that link, really usefull looking site, still no closer to figuring out problem though, as I seem to have 'most' of the bits that I'm meant to, oh well, if it works why change it? The rest of the bikes a bit rough any way so I won't worry!
What it did tell me is that the bike's probably an '85 (drum rear brake) not an '86, unless US specs differed from UK.