3276.8 is what I get assuming its 2:1 reduction and that seems right as if you send 2000 pulses per mm,  as you currently have in motor tuning for Z, and command a move of 50mm you will get an axis travel of 30.5mm

Hood

Thanks hood, I'll have a play tomorrow.

Thanks Hood, those figures worked spot on!!!

My Z Axis is reversed though, I've revered this is the software and now working as it should. Just the motor tuning today for me.

Yes for reversing an axis with the CSMIO you have to use the Reversed option in Homing and Limits page instead of using the Dir active state. No big deal but took me a while to work out why I could not reverse an axis on their Step/Dir controller as I had always done it via the Dir active state

Hood

Yes I found that option and it works a treat. I have tuned all the axis, but something has gone wrong with my z motor, jammed solid. I've got spares so I'll strip it and investigate.

Ok the pid motor tuning page, I have tuned the motors so they have an error of about 70-80, is this regarded as a high (bad) or low error count?

 With yours being 2000 steps per unit then that works out to 0.035-0.04mm so could be better but not too bad.
Hood

Also just to put this into context, that is at rapid speeds and you will almost certainly get a much lower amount when at cutting feeds. To get an idea you could test it out by going into the PID Tuning and set the move speed down to say 10%  (see 1 in pic) and also set a move amount, see pic of where you enter that value (2). For example if you look at the axis position and then decide on a move that would be safe and enter that into the Position box. You then want to press the apply (3) to zero the error (6) and if you choose the option of double move (4) then when you press Start it will move to the position you entered and then back and you will see the error.
 I suspect you will be a lot lower and that would represent a feed of 500mm/min

Hood

Thanks Hood, I'm back on this again now, I'll have a go at the above

I'm still yet to try your tuning test above, I now have bigger problem

When I run some g code as a quick test (with spindle motor stopped, the main RCCD in my workshop trips after a few mins. So I rewired the power supply going to my rotary phase converter to before the RCCD in my workshop,
Now when I run the mill, after about 30 secs it trips the RCCD in the house (which it's not connected though).

In my house I have coming out of my mains supply meter I have two pairs of 16mm2 cable. One set goes to my house consumer unit, and the other out to my workshop.
 
I don't see how something in my workshop could impact the RCCD in the house, any thoughts?