my 2008 UK (London + Oxford) & Italy (Rome + Assisi) trip 

I've spent 2 days in London, 1 day in Oxford, 11 days in Rome and 2 days in Assisi.
P.S. Buckingham Palace only open to public in limited days, pls refer to its official webpage for details. And Assisi would have St Francis feast day celebration on every 4 Oct, many big events would be taken place, please reserve your hotel room in an early advanced.