https://en.m.wikipedia.org/wiki/Left-_and_right-hand_traffic
If you read it, you'll notice that right hand traffic is the most common worldwide by a huge margin.
You'll also notice that in ancient times people were driving in the middle of the road and when crossing, they kept the ... right side of the road, so please stop with this absurd assertions.
And once again U.K. was, is and will always be in Europe, but decided to get out of the EEC, which is something different.