Yes, I was guessing that an under-pavement isolator might be difficult to implement but thought this might be worth a try.
Here's a photo of a fine example of the type of column we're trying to save:
There can't be too many of these left on Britain's streets now but here in Reading we still have over 100 left, all made by local foundries. This particular one is a rarity in that it isn't next to the kerb so for this it will be somewhat easier to add an isolating pillar. I'll try adding a gallery later. In the meantime I hope you don't mind me giving our campaign a plug - it's at
https://loveyourlamppost.wordpress.com.
The town also has nearly 200 mid-20th century Revo Moseley columns that we would also like to see kept - the good news is that the council tells us it intends to keep as many of these as possible as they have a low-level door.
The council's contractors have managed to fit Holophane V-Max lanterns to a few of these swan necks by cutting off the finial but are finding the installation unreliable so don't want to do any more. It's not aesthetically ideal (personally I'd love to see a little round top-entry lantern on that finial, perhaps an AC 730) but they have been trying at least. I did some research looking back at historic street photos, and the choice when the gaslights were replaced was ESLA reflectors or small round lanterns (perhaps GEC Z5590s).
So we're just trying to find out if there's a safe lower cost option to keep the original gaslight columns in light - they've survived over 100 years and are probably going to stand for a good few more if they're allowed to. If anyone has any suggestions I'd love to hear them.