Update.. we were advised that an electrician would come back and check the wiring.. The gas fitter gave the impression that he would just fix his temporary mains cable into place..
Oh my god! We had a full test of the consumer unit, earth leakage, bonding, the whole house.. The works.. And he said it was an easy job.
Can't say I'm anything but impressed with the whole thing.
Dread to think what 2 -3 hours of an electrical engineers time is worth.. Or the actual job e did.