Thanks chaps.
Oswaldo - the glazing is fairly easy to be honest. The slightly tricky bit was making the quarter round moulding - but you may be able to source that. You then cut a rebate for the glass, put some glazing putty (not sure proper name but comes on a reel and is very easy to apply) in the rebate, add the glass, seal the void with some low modulus sealant, mitre the beading and nail it in place. Not sure a uPVC door is more draft proof to be honest.
Cheers
Gidon