Not 100% yet, Jo. I practiced cutting an m14 x 1.5 internal thread last night after our discussion and it went OK. So as you say, changing the headstock might not be the thing to do.
Ade, long gone are "free periods"! They are now Planning periods and must be spent in work! Lunch is 45 mins :-(
Cheers for your offer phil. How is the CNC running?
Andy, thanks also for your offer... I'm sure I'll sort it, tbh, it was only a question based on can the chuck key be calculated so i can order online and although you and others have offered possible methods, it seems like the focus has been on me going in store and finding one suitable trial and error.
So thanks for everyone's advice, however positive , negative or agressive... I'm sure ill get it sorted. All the best