Not entirely sure I agree with you about the bitsa theory, Jasper. You could re-badge your 1999 Foggy as a Corser, but you wouldn't have the box. I'd be very wary about paying for a 1999 Corser without a box, given the prevalence of 1999 Foggys and the fact that you'd only have to change a couple of decals.
Maybe your bike was originally a 2000 Hodgson (hence the box) and somewhere along the line it's been treated to strip and rebuild with Foggy decals and custom paint. Quite why, who knows???