In retrospect it's funny that the two people that pretty much no one wanted on the list (Lennon and Di) were the ones that made it. Kind of silly since it's far too soon to see if they will have any long standing impact on Britain.
My vote, and I'm bucking the trend here, Charles Darwin gets my vote. I'm horribly biased though, being a biology degree holder and all.
'Ole Chuck gets a really bad rap as most of the people give him all the baggage that comes along with evolution. Darwin did not come up with evolution, in fact, evolution was never even mentioned in Origin of Species (at least not in the context we take it if it was). What Darwin contributed was the theory of natural selection, the basis which underlies evolution. It's beautiful, it's elegant, and it is the window through which we view all of modern biology. Religious fanatics have tarnished the legacy of this great man, and his theories don't even directly conflict with Creationism...in my opinion they make a stronger case for a supreme being, if anything. Errrrr...rant over.
Also interesting to note is that if Darwin wouldn't have come along and published OoS, a man by the name of Alfred Russel Wallace, a naturalist and big game hunter, would have been given the credit (and baggage) or the theory of Natural Selection. Both Darwin and Wallace came up with the theory at about the same time and even had correspondence about the subject...Darwin just beat him to the punch (and rather underhandedly, I might add).
It's actually a bit worrisome that the human race is no longer under the constraints of natural selection, but instead under social selection...but that's a whole 'nother rant.
While Darwin is pretty high on my "cool" list, my biology superheroes are Watson and Crick, the gentlemen who discovered the structure of DNA and revolutionized genetics. Crick was British...he should be on the list