The EGR its telling me its stuck shut but I have put a new one on and it just doesnt do anything, not moving at all

The mk3 doesn't allow you to command the egr open, monitoring it with forscan I can see when its been told to open and there's no movement at all

Focus 2013 TDCI 1.6L Duratorq CR TC (115PS) and the code is P042F EGR stuck closed

This is probably a really stupid question. I am testing the wiring to a component, I got someone to took it up on Autodata and says its a ECM earth circuit and should be 0v with the ignition on. If I test it at the block connector while unplugged its 0v but if I plug it in and test its 12v. Does this sound correct? or should it be 0v if unplugged or plugged in?

I don't know if you know, but lots of people don't know how to use a voltmeter. A very common mistake is to think it works like a test lamp but if you do then you're wrong.

A voltmeter measures potential difference. That is the difference between two points of a circuit. It does not measure nor does it indicate the presence of current or otherwise. When it shows 0v it's telling you there is no difference between your red and black probe. When it shows 12v it means the difference between the red and black probe is battery voltage. The voltmeter is an excellent tool for identifying high resistance under load and does not know how to lie. Don't fall into the trap of disbelieving what it tells you like so many people do. It's not the meter that's wrong.