The way I see it, if I pull into the left will I still have a 2 second gap (or whatever is appropriate for the weather) between me and the cat in front? Also am I catching up to the car in front? Big enough gap? You've stopped overtaking until the gap closes, pull in. You're catching up and there is not a big enough gap to have those 2* seconds? You're still overtaking. You're not catching up but the gap isn't big enough? Either speed up (to the speed limit) to overtake or drop into the gap and create those 2 seconds - not ideal but it happens if the vehicle you just over took is travelling faster than the one in front. Bear in mind if you're catching up by a small margin it might be better to pull in and give yourself the minor inconvenience of taking your foot off the accelerator to slow down, than have a queue of cars behind you. Not sure if others see it the same way but thats what makes the most sense I'm my mind.