(Several year ago we were due to have a SMART gas meter fitted, but we were told that it needs to be screwed into the surface on which it was sat, so installation was not possible.)
Best answer by Transparent
The situation with electricity is easier to understand. Traditionally your 100A incomer fuse and any meter(s) were screwed to a board. These items and the board itself were the property of your DNO (Distributed Network Operator). You obviously mustn't tamper with the fuse or meter(s) because they have a metal seal to prevent you doing so.
Moreover, you're not meant to attach anything else to the board either. I once got into trouble for fixing a pair of anti-surge protectors on Western Power's piece of wood!
I've noticed electricity Meters and Fuses in all sorts of strange places when I've visited old properties. I've even seen one woodworm-riddled board swinging from the ceiling beams in a converted barn because the wall it used to be fixed to had rotted away behind it!
Gas meters are bit more tricky. If they're in a box, then this too is regarded as the property of the relevant network company (Wales & West Utilities where I am). The box might be embedded in a wall or half-buried in the ground. There are different types.
Older gas meters used to just sit on the floor in an under-stairs cupboard or a pantry. But even there, the network company could insist that it was kept clear of clutter and not boxed in because they can enforce having access to their meter.
I've never met a gas meter actually screwed to an antique stone table. But I'd love to see a photo if you'd like to post one here please :)
If an installer insisted that a Smart Meter must be screwed to something, then I'd be tempted to fix a 20mm thick piece of ply to the stone table with four blobs of silicon mastic on the corners. He can then screw into that!
But it still seems odd to me that the gas Smart Meter needs screwing to anything more than is used to fix your existing meter... which I assume stays in place because of the rigid pipes it's connected to?
Give us a bit more description of the existing set-up, preferably with a photo, and I'll try to comment further.