Robert Hooke accused Newton of taking credit for gravity from him, but it was Newton who supplied the mathematical proof for the theory of gravity. Hooke to be fair was also a great scientist with a number of important ideas and discoveries, including the idea that light was a wave, and Hooke's law which describes the behaviour of springs. Hooke should be in this list. Hooke and Newton seem to have detested each other, sad in two such great scientists. But in the end Newton's achievements were greater, because he could supply the mathematical rigour as well as the experimental skill.

In the end I think its difficult to look past Newton and Darwin for this, and maybe Roger Bacon if anyone thinks they really know what he looked like. Newton as has been mentioned has already been on a note, but that note is now discontinued, so it shouldn't rule him out. These are three of the four outstanding British figures in any field of the past thousand years, the fourth of course being Shakespeare.