Well I'm a bit overwhelmed information wise – in a good way! Thank you all very much. What a great forum.
Since I ordered the Harold Hill book, I have seen some criticism re dated on approach and content? – So the Sparey's will be on the order list. Thank you Hopper, Howard & Larry.
Thor and Bob, thank you for those links, book marked and will be reading up. – In fact I have copied this thread to a doc so I can refer easier to it 
Neil, I take your point and won't go spending on lots of tooling until I understand the basics of what I need.
If the external 3 jaws work out on this original 80mm chuck I will post back in case of interest.
Many thanks
Chris