Thank you for the reponses. If it wasn't for the missing bolt cover lugs, I would have to come down on the side of leaving it alone or restoring to military specs as far as possible. I know the lugs could be restored, but finding a welder skilled enough, and what that much heat might do to the metallurgy of the bolt, make me think that would be a bit too much of a stretch.

Well, it's not like I'm going to start tomorrow, so we'll see what more information turns up. The counterbore of the muzzle comes first I guess. That and finding a correct magazine cutoff. It does look quite a lot like a "No.4 Carbine" as described here in your thread Sarg: http://forums.nitroexpress.com/showflat.php?Cat=0&Number=150485&an=0&page=0#Post150485 (The catalogue page seems to be gone now?)

I do wonder if a UK gunmaker would have sold it with a cut down stock from a "Long Lee" (having the relief for the long range peep sight)? The way the front swivel hole is off-center looks like a home job as well. Almost makes me wonder if a previous owner of long ago might have removed the carbine forend complete and replaced it with this one rather than cut the original down. Not likely to be found now, though I will make enquiries.