Yup, watch out for the unusual situations. Standard traffic is usually all right after a few hundred meters, but as most said, as soon as you encounter some unforseen difficulty, your "right side of the road" reflexes take over while you mind tackles the problem, and the next thing you know you're facing a lot of angry car drivers who are not extremely happy about you being on their side of the road. That or an angry policeman.
Oh, and be careful about one strange thing when driving an UK car: you tend to forget that there's a lot more car on your left than you're used to. What I mean is that it seems you use the same distance between you and the left side of the road that you'd be using with a French car. If you're lucky, you're girlfriend will just scream from time to time when you get but a few inches away from a car/tree/wall. If you're not, you will hear a loud crash and wonder whatever happened .
Every procedure for getting a cat to take a pill works fine -- once.
Like the Borg, they learn...
-- (Terry Pratchett, alt.fan.pratchett)