I have never had to replace an old imperial back box for the simple reason it has imperial threads.
So far I've always be able to re-thread the holes, and M3.5 screws have fitted.
As said, the biggest issue is whether the back box has horizontal fixings for a new socket.
Get switched single sockets this time.
Or, as suggested, fit doubles. As said, you will need a new back box in this case.
HOWEVER, 'CONVERTA' sockets are flush doubles which will fit a standard flush single box.
This may be the simplest solution.
Would save a lot of damage.
If you have some horizontal fixing lugs on that back box, you can even re-use those old screws - the CONVERTA has little plastic tabs which will cover those old screws.
You may have to buy some (large) earth sleeving IF the earth wires are bare. Wiring of that age sometimes doesn't have the bare earth sleeved. You would need green and yellow sleeving.
Ye Gods - what kind of animal thinks that's the way to paint walls?
Not necessarily - the lugs at the top & bottom can easily get in the way of modern replacements.Looks like an old MK. I presume you mean like for like because the screws are vertical? If so have you checked the back box it may have lugs on the side as well, you could then use any replacement you want.
Unless the old screws will go through the holes in the faceplates of the new sockets.Accessories are usually held in place by two 3.5mm screws, one on the left and one on the right. The sockets you have there are *very* old and current sockets will need new back boxes.
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