I'm not sure how accurate the speedo is on my golf, I had a GPS with over 8 satellites & there was near on a 10 mph difference! I did have a feeling 80mph felt slow for 80mph.
I got caught speeding last year, I never do over 100 any more now, far too risky, plus so many other fools on the road, imagine some tw@t doing 50mph dawdling along & your speed testing at 150+??