You are both tantalizingly close!

OK let me summarise.
I want a city name, not a university name.
The city does have a university.
The size 8 city does NOT refer to the number of letters in the name. (You've been doing crosswords too long!) This is a Civ site, so it refers to the size of the city as if it were on a Civ map! You should hang your heads in shame! Actually this city is slightly less than Civ size 8 at night, but its local government website claims that during the day, Monday to Friday, it grows to Civ size 9 because of all the commuters - nearly 50% extra!
Did I hear mention of William Wilberforce? He may have gone to Cambridge, but where did he grow up? And which city did he represent.
And Andrew Marvell? Sounds right to me! But why was Marvell "unofficial"? And who is the "nearly man" PL?
Extra clue: Incidentally, Wilberforce and Marvell both went to my school. We're talking about my old home town here.
And well done for knowing of Silver Pit. Once just a small trough in the North Sea, now well known to drillers. Position specified absolutely correct. So where is 50 miles west of there?
And don't forget: two rivers. The city is "named after" one of them. (You'll see the reason for my quotes in due course.) And the name means "the deep one" (or perhaps my Old Norse is better than anyone elses - but hey, it was in brackets in the original question).
My apologies if this extends beyond the bounds of a normal geography quiz. Most places have a history and are often best described by their history. And I guess it's my personal history and geography I'm describing so I'm biased. Makes a change anyway, doesn't it.
