Well, as i pointed out to begin with, i've heard differing times, so i asked.
How long is a piece of string?
But from County ground on a bus should be just under 2 1/2 hrs, in a Car should do it just under 2hrs. unless you hit Cambridge at rush hour in which case add at least another 1/2hr to that time.
It's over 100miles and the A14 can be a b*tch of a road at any time of the day