I think just about everything was covered here. I sit in the middle of the lane if the lane is clear ahead of me, but sit to one side of my lane slightly if I'm following traffic. It's to keep myself visible in their door mirrors, but mainly so I've got an escape route, should everyone suddenly throw on the anchors in front. It can be particularly windy in places, especially when dealing with large vehicles. One thing not mentioned, is to keep double checking your speed when you leave the motorway. After a prolonged period of high speed riding, 30mph feels like walking pace.
