I now have one camera and one flash, rather than a combo unit!
Needed wife to hold camera and flash while I pressed jewellers screwdriver down hard and turned screwdriver with pliers! Screws were pretty tight but mostly the angle leaves no where to grip the screwdriver.
Have removed the pin and spring. Interestingly, the locking mechanism that clamps the flash to the hotshoe still works fine. Combined with how tight it is sliding into the hotshoe anyway, the pin (which is quite a solid item.. don't go trying to bust it off!) is complete overkill!
Regards, Nige