On a sensible health and safety note I think it is probably time we started driving on the right hand side so we are in tune with the majority of the world.
Sweden switched in 1967 when they had a population of around 8m people spread over 447,000km2 . At that time they didn't really have much traffic and very few OAPs that would be easily confused. I don't think they would be able to do it today even though they still only have about 10m people there, many more are much older and easily confused.
The UK is about half the size of Sweden at 224,000km2 but we have 66m people living here so there is a lot more traffic per mile than Sweden will ever see.
We would see a lot more stories about people on the wrong side of the road, made even worse as people have their steering wheels on the wrong side until they buy new cars. Imagine the carnage as boy/girl racers pull out from behind a truck to overtake but hadn't seen the truck coming the other way.... Its a risk we take when we drive abroad, but we are on holiday and generally not running late for work etc so less likely to take that risk.
Then theres all the car/van/bike headlights that "kick-up" to the left that would need stickers, or new headlights, to avoid dazzling people coming the other way. The road signs that would all need to be moved/replaced to show the new junction layouts etc. It would cost more than Brexshit and cause more deaths too.
Make the rest of the world adopt the correct side of the road instead