Data cable is Cat5/6 – 4 pair is a about the same a BT telephone cable coming into your house and 2 pair is half the size. You only need one pair to connect a CT clamp but, very much depends what they have on their van.
Demand-limited (load curtailment) charging covers CT clamps and is refered to in the IET Code of Practice for Electric Vehicle Charging Equipment Installation
Its a safety feature at the end of the day, as the clamp monitors the load going through your house. If the clamp detects the load is close to exceeding the total load the house can handle, the charge rate of the charger would be reduced.
In the event your cut-out were blow, due to overload, the HSE time scale for the DNO to replace it, is up to 21 days and your likely be billed for the work.
Whats deeply concerning is, no checks were done when they came out and swopped over tothe Ohme charger. They also proceeded to unclip the CT clamp, as photo’s show it was connected prior to the changeover. They then either didn’t notice they had left it unclipped or most likely realisised its wasn’t compatible Ohme, as no wifi is available and thought fook it no one will notice – Cowboy!
Did they issue you with another test certificate once they had swopped over to the Ohme charger?
Insist on a hardwired one being connected, if for only safety reasons!