As you may know, 2009 is 'Darwin Year' as it is 150 years since On The Origin of The Species was published. In response, the market for Darwin items is strong. A recent highlight being this portrait by Julia Margaret Cameron that sold for five times its estimate at £22,000 in Aylsham. Signed by Darwin in the mount and inscribed From Life Registered Photograph Copyright Julia Margaret Cameron. It is a variant on the most commonly seen and reproduced Darwin portrait by Cameron.
Exploring the English Heritage site recently I found that you can take a tour of Down House, the Home of Charles Darwin. You have 360 degree views of his study, billiard room and dining room and can click on particular items for a little more history. It is a much cheaper option than flying to Kent, although I did want to see the view out the window. http://www.english-heritage.org.uk/Darwin2009/index.html