Greg, Have just had a look at the fork bilamms (lug extensions) on your blue Bob Jackson. They are identical to the "Magnum Opus" S/S bilams (extensions) or the "Magnum Opus "MK11" Lugs. How do I know this they have been identified from Hetchins lug pattern drawings my late Father-in-Law kindly donated at his own expense to the Historic Hetchins web site. Wilf Hollis (FinL) known to everyone as Reg was a member of the Bermondsley Gospel CC & Clapham and knew Jack, Claud, Bill and George and did work for them all.
Thats all for now. Keep those wheels spinning, in your memories if not still on the road. Be lucky Mick Butler Huntingdon UK.