Actually, I don't think there is much difference (in law) at all. With gas, the accepted industry operating procedures are that if an RGI finds a dangerous situation they must recommend disconnection and do so with the property owner/responsible person's permission.AIUI, and as others have suggested, there may be a legal problem in that, unlike the situation with gas installations (and with DNOs), I don't think that there is any legal basis for an electrician 'locking off' an installation if (s)he considers it to be unsafe without the agreement and consent of the customer.
If permission isn't given, then they ask to turn off the main gas supply valve. If permission for that isn't given then they can call the gas supplier - who will disconnect the supply (either by capping the meter, or if access is refused, by digging up the street) if they agree the situation is dangerous.
Only that last step is done without requiring consent from the property owner/responsible person.

