that's a crazy-good price for a frame that has a small but rabid fan-base, for good reason!
Assuming no damage or other downside...even if it was something made later by Whitcomb, I bet still a great riding British bike.
There was (is?) a contributor to this C&V forum who's based in Tokyo (but British) and was something of a Rotrax collector, if you search early posts for "Rotrax" I bet you'll see some pix of his machines