Best advise ever: (found via Google)
"If you are planning to visit the UK and happen to come from one of the many countries that drive on the wrong side of the road, the following advice, direct from the Ministry of Transport, is for you:

“Visitors are informed that in the United Kingdom traffic drives on the left-hand side of the road. In the interests of safety, you are advised to practise this in your country of origin for a week or two before driving in the UK.”"

Really only about 1/3 of the world's population drives on the left side of the road, I still stand by my statement that the majority of American drivers are terrible however.