Hi Graham,
I'm still having a real thick moment here

I thought I could zero with any tool that had been entered into the tool table.
i'e tell the machine I'm using (say) T6, zero z with that and call the TLO from the gcode.
But, thinking about it, I normally use my T0 (blank tool) to set z zero, but when using another tool I zero, I'm setting up in machine coordinates (the XYZ have red surrounds) not work coords (green surrounds) i.e I have not set Ref ALL. (have no home limits at the mo)
So if I was to ref all and set z with say my T6 and calling the TLO from the code, would that fix it for me?
I can't get to the machine to try for the next few days but will give it a try on my return.
Thanks for your help
Derek.