A friend of mine was born over in the UK and had never been back until he was about 25. He went with his wife, his parents, and his US born sister and her fiancee'. After they got over there, they wanted to go to where his parents grew up, so they rented two cars and the plan was to meet up in whatever the tiny town was they came from and he was born in for the night, after doing what they wanted to separately during the day. My friend's parents were just awful drivers, so he and his wife drove. She wasn't comfortable at all, so he did most of the driving. When it was later in the evening, they stopped for dinner at a nice place, and had a decent meal. He was very tired from driving all day, and the food kicked in and he made a left turn into the right lane. And instantly hit a "lorry" which had just pulled onto the road. Nobody was hurt, but the car was a mess, and the rental company sent out a replacement. That car wasn't driven much, as they were scared he would mess up again. When they left about 5 days later, he was near Heathrow and did the same thing again, but this time didn't hit anything. Scared everyone though.
When his parents got pretty old, he took them back again, for what would surely be their last trip, and it was. That time and everytime since, they have hired one of my friend's cousins to drive them around. Apparently he does pretty well taking right side drivers around. I was thinking about going over to London, and there is no way I would drive, as I'm sure I would screw up and get into a wreck, going on "autopilot" when I got tired..