If you are travelling at the National speed limit, then the berk behind you is going to be breaking the law by going faster. If the lane next to you is free, just pull over and let the idiot go.
If you are in a line of traffic, moving at a speed that is suitable to ensure the traffic in your lane is keeping pace and there are 2/3 lanes to your left and they are all full, you have no obligation to move. So if this is the case, even if you did move over, where would the idiot go? He'd only be able to take your space and then he'd be tailgating the person that was in front of you.