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Octopus
Ukpn were really helpful, it was easy to get to someone who knew their stuff and the came and replaced the whole cutout pretty quickly, on the other Hend the energy supplier didn't have a clue, eventually agreed to fit an isolator at a cost, then forgot to charge us. So i think it must gf depend a lot on your local area.
UK PN are always really helpful ............... but its not them we have to deal with for isolators ...............