Sitting in the middle lane for no good reason is a very British thing in my experience. Having driven on the continent a lot I've never seen it to the same extent anywhere else. Probably because you get tailgated within an inch of your life if you try it.
In America you get tailgated non stop regardless of what you do. Yanks are the worst drivers on the planet, including 90 year old Hong Kong taxi drivers.
Then they dawdle around in the middle lane, gradually getting up to speed for about a mile after the 50mph limit has ended.