very interesting: no doubt the lugs are Nervex, but the rear sockets on the headlugs, and the entire seatlug, is not the usual Nervex pro pattern.
I think that's the angle of the seatlug, something Nervex did...and the BB shell is very different, it might be a Nervex, too but not like any I've seen. The whole thing has a "British" look to it, however, a 27.0 seatpost points to either plain gauge 531 seat tube, or...track-specific tubing (??) or Columbus SP or Aelle...I doubt the last 2. No idea as to that stay cap, very much unique!
Did you check the steerer for "rifling"?