Vic,
Good to hear from folks across the pond! Phil Gibbs, CAMILLUS moderator and our of the engineer on the CUDA QUICK ACTION project is from England also. Small world indeed. Phil informs me that the clip screws on your knife are '2-56' thread size. He does caution that the screws are 'lock tite-ed' in place, and he says he would not recommend replacing them. But if you really want to, use a 2-56 size, the same lenght as the one's you remove from the knife, and apply lock-tite. Thanks for being a customer!
Cheers,
Will Fennell,
CAMILLUS CUTLERY