Not going to happen. UK and Japan are both island nations (as are Australia, New Zealand, and Indonesia), so there is no pressing need to change. And India is probably too large to change.

And Pakistan won't change because the camels wouldn't agree.

That's the story I heard, anyway. They were considering the change but then someone pointed out that the camel caravans continue through the night with the driver asleep on one of them and the camels know which side of the road they go on and if you tried to argue with them about it, well, they can be cantankerous, apparently.

That's hilarious. I wonder how traffic changes affect dogs and other animals that cross the road often?

Switching today would be virtually impossible. Just think of all the freeway interchanges that would have to be rebuilt, costing tens or hundreds of billions of dollars.

I think most interchanges would be fairly symmetrical. Although a lot of bellmouths at junctions would need to be changed to accommodate HGVs. And lanes approaching roundabouts would need to be moved.