I have recieved the info back from the supplier.
Everything is okay, I have to send them my speedo cable to have a Hall effect sender fitted to the standard cable and my current fuel sender to be calibrated to the VDO gauge.
I am in the middle of my masters degree exams and have my first kart race this weekend so I haven't had a chance to get the parts off the car. Should have this done in the next 2 weeks.
They said it should be approximately 1 week to get these 2 parts modified/calibrated. After that it's straight into getting these into the car.