_No_ it's not true, although a lot of people drive faster than they should.
> On motorways in 2009, 52 per cent of cars exceeded the 70 mph speed limit. In addition, 16 per cent of cars were recorded as travelling at 80 mph or faster.
> --source
In response to your edit: the majority of people drive _below_ 80mph. only 1 in 6 drives at 80mph or over.