I think that has to be it. When I first started trawling for a match, I thought it didn't look too disimilar to one of these:
- Bob Damper's Bates Eucadian, as featured on Classic Lightweights.
Same Nervex lugs, lots of the same equipment, non-parallel head and seat tube angles, position of pump pegs and cable braze ons all sold it. But the serial number fits well with the known Macleans serial numbers, giving it a late 1958 / 1959 build date. That fits with Ned's estimate, and although I don't know the first thing about Nervex serial numbers, the one on the bb shell does end in 58. There's a similar Maclean on ebay at the moment - same drop outs, same lugs and happily, worn decals in place too.
Just got to work out what to do with the thing now. I guess it's had a repaint - maybe at the same time the Huret Svelto went on? - as it seems unlikely that the transfers would have vanished completely.