I agree with you there, Eddie - I had a similar driving instructor as he was actually a truck driving instructor as well. I then went onto do advanced and have been on defensive courses (took my staff on one - and that included oodles of driving and that you can actually go faster than 70 in front of the police if they see you "driving." What does this mean, - moving out into the third lane, truck in front of you, someone in the "tunnel" between the truck and barrier. Let that car go through before entering (as you have no clue what could happen) and then, once clear, accelerate up (to 90+ if necessary) and get through asap. Slow down and move back.
This came from ex-motorway cops who were the instructors and at TRC near Reading....what they are after is the loon sitting in the second or third lane driving at 85, probably on cruise control and staring into oblivion, thinking about his/her sex tonight or the shopping list. They are the danger.