I can tell you that Corby, where Bob Mitchell cycles are based, is a pretty small town and I'm guessing that Bob Mitchell cycles didn't make the bike; they sponsor a small team of racers and I'd guess this frame is just painted in their colours.
If you don't feel like phoning they do have an address and you could write to them:
Bob Mitchell Cycles, 80-82 Rockingham Road, Corby Northamptonshire NN17 1AE
Bet they'd be pretty happy to tell you something about the frame.
The other option would be to pop a post on
http://www.londonfgss.com or on
http://www.bikeradar.com. The former is the london fixed gear forums but folks are there from all over the UK. The later is a website run by Britains largest bike magazine and will definitely have folks from Corby on it.
Worth a shot.