The "middle lane" on a 3-lane motorway is for overtaking drivers who are in the left hand (UK) lane. And so on. The Highway Code is quite clear, you should drive in the furthest left lane that is safe. In theory it would be possible for a member of the middle lane owners' club to be fined for driving without due care and consideration, if he were obstructing other traffic (who should NOT overtake on his inside) but if he were driving at the speed limit it is hard to envisage it occurring.

The legal limit on single carriageways is never more than 60.

Having said that I am pretty much a press-on driver so rarely get tailgated, although if I have the caravan on the back and am doing the legal limit (plus maybe a mile-an-hour or two, just for luck) I do get frustrated by drivers who are manifestly champing at the bit behind me.