I wonder if ....
While looking for something entirely different online I came accross "Bottle Lamp Kits" - around £13 a pair and available with ES and SES bnulb holders. Essentially its a plug, inline switch, total c.2m cable leading to a side cable entry moulded bulb holder with a stopper on the bottom to fit the bottle of your choice. All asembled as one thing. Amazon do a few brands, claiming to be CE approved (which I am pretty sure is still valid post Brexit, UK approved runs alongside but hasn't yet replaced it). An Ebay search comes up with a bemusing range of items and prices, a rabbit hole you can disappear down. Maybe local hardware shops sell them as well, I've not seen them before.
It's not as elegant as running wires through a table lamp, but is fuss free as long as you make a 16 - 19mm (bottle neck sized) hole in the wooden item, maybe 40 or 50mm deep but can be 'blind'.
I wonder if you had one assembled for display purposes, but sold it as the lamp base plus the kit in the bag in which it came - all the customer has to do it unwrap it and push it in - you avoid any regulatory risk.
At £13 a pair, £6.50 each, they are a lot less expensive than many of the kits sold to woodturners and there is much less work to do. .I've never sold a lamp but ones I have made for my own and family use would have looked fine with the bottle kit, the wire just hangs down the back. You wouldn't win a club competition with one perhaps, but for those who sell it might be a good way to reduce liability.
Thoughts?