while UK 230 volt 'lightbulbs' were bayonet?

Edison Screw is simply inferior to bayonet. The heat from the bulb tends to
weld or corrode the bulb to the carrier due to the large contact area. Every
ten bulbs, the bulb will simply shatter when you try to twist it out,
leaving the carrier welded firmly to the bulb base with shattered glass
shards sticking out (and a hand covered in blood). It also has a huge
neutral contact which is frequently connected to the live instead.

Christian.