In the UK the speeed limit is 30mph on regular roads and 70mph on motorways (highways) but the police usually practice an unofficial policy of allowing “10% +2mph” over the speed limit before stopping you.
Incidentally there has been this week talk of raising the motorway speed limit in the UK to 80mph in line with Europe where it is either 110/120/130 km/h (75-80 mph).
But based on the policy of allowing “10% +2mph” over the speed limit before stopping you, it is 80mph already before they will stop you, and seeing as they said that if they do increase the limit to 80mph they will not allow ANY higher than 80 and will stop even at 81, I fail to see what will change!