I asked my local DNO this question, this is the reply:
In terms of jurisdiction, SSEPD as distributor is responsible for the incoming service and cutout, including the company fuse.
The incoming tails,or rather the tails from the cutout to the meter are the Meter Operator's repsonsibility. I do not work for the MOP, but I would assume that any remedial work on these tails would be organised with the MOP by the supplier at the property.
The outgoing tails from the meter to the consumer unit are the responsibility of the customer and can be worked upon by any qualified electrician.
If the meter seals are cut, or the company fuse is pulled, we would add a site note against the property on a system called CS, listing the electricians name, mobile number,company name and trade association number. Any NICEIC, ECA, NAPIT, ELECSA orSELECT registered engineer is allowed to pull the company fuse or break company seals.
Temporary seals, used to tag works carried out, can be obtained from the closest regional SSEPD depot.
Seems straight forward enough?