Ok so I have made progress.....
If I ref the Z then I can do a tool change (it wont go to the Z position when M6 is called). Then with out any tools it works perfectly.
However when tools are added then sometimes it works perfectly and other times it comes across, grabs the tool then sticks. Pushing the toolchanger seem to get it going. I've checked (and adjusted) the limit switches so am stuck again....
Any ideas why M6 doesnt put the Z at the home position~?