Info so far: it's a model P18T, I think. The T indicates flat bars, apparently, C being drops. Lowest gear is a 34, it just looks so big because it's a 13 or so to 34 FIVE speed, them's big gaps between gears, them is...
Done some basic work with a rag, just to see what it looks like. Will need advice about rust, but none seems to be more than surface, biggest patch of which is around the RD where the cable has rubbed.
Mudguards come up like mirrors! Removed the UV-rotted ally-framed skirt guard. Bars by Philipe, hubs by Maillard. Serial is Y411 29065. Best guess early to mid-80s. Also, with 5-speed and cottered cranks, this may be a little older and/or at the cheaper end of the range, which certainly had 10-speeds with alloy cranksets, for example.