The most famous aspect of driving in the United Kingdom, for most foreign visitors at least, is of course that the British drive on "the wrong side" of the road - i.e. on the left hand lane, and the driver sits on the right hand side of the car. It takes some time to "reprogram" the mind to think in the opposite sense at junctions and on roundabouts and motorways, so the main thing is not to drop your guard 2 or 3 days into your visit, as this is when most accidents involving foreign drivers happen. You can also do some online practice before you arrive to familiarise yourself with driving in the UK, try some practice learner driver theory tests. If you are from the USA or Canada - bear in mind that most cars are manual transmission which can further complicate matters - your car rental company will give you a "stick shifter" unless you specifically ask for an automatic when you make a reservation.
