The Bank of England is asking the public for recommendations for a scientist to go on the £50. This is before they give the honour Rosalind Franklin because she is a woman. Mind you, if that is the route they chose then Margret Thatcher who started her career as a chemist would be my choice.

The Register has a great list of contenders.

— update —

The Telegraph also has  a nice review of the contenders. Although I am a physicist, I am swayed by the argument of @Michael Staples who suggests that the discovery of DNA must surely put Crick and Franklin into the front running. Who will you choose and why?