[Nonfractal]

After some googling M3 brass inserts are the equivalent to 4-40 for those using metric,

Picked up 25 inserts and screws to suit for a £10, should me through for a while and if I go through them quickly, I'll buy in bulk next time round.

Thanks for all your advice on this thread and again, apologies for hijacking 

Rob

Rob, where did you source these? 
Alan