Rightly or wrongly, I never go into lane 3/outside lane to overtake members of the middle lane owner's club, I just pass then on the inside. If I had room to pass on the inside, then they had enough room/time to move back themselves & I'd have passed in lane 2.
Except on the M25, the undertaking maneuver is illegal and you will receive a penalty notice if seen doing it I'm afraid!
This one goes down to TrafPol interpretation of both your driving and the law...
Highway Code Rule Number 268:
"Do not overtake on the left or move to a lane on your left to overtake. In congested conditions, where adjacent lanes of traffic are moving at similar speeds, traffic in left-hand lanes may sometimes be moving faster than traffic to the right. In these conditions you may keep up with the traffic in your lane even if this means passing traffic in the lane to your right. Do not weave in and out of lanes to overtake."
I have asked this question to Hampshire TrafPol in the past and their answer surprised me somewhat!
What constitutes a queue of traffic?
Answer: 1 Car!!!

So essentially, and this was the answer I got, if you are travelling at a constant speed you can pass on the inside, as long as you aren't weaving from lane to lane.
Personally I wouldn't want to push my luck with it but...