The national speed limit for the motorway (unless otherwise stated) is 70MPH,
iirc, so I'm quite happy to sit at that, weather/traffic permitting.
The speed of the vehicle in front of me will define whether I am to overtake or not. If a HGV is travelling at 70MPH, why should I overtake it? However, if it is travelling significantly slower than this, I will overtake.
I can see your point, of course - you were overtaking. Increasing speed slightly is part of overtaking, however 85MPH is
excessive in my opinion. Perhaps not yours, or others.
Your questions do not, however, justify speeding.