As I mentioned below, if you expanded the list from 10 to 50 or 100, the US list would be a Who's Who of start ups, and the Euro one a Who's That? Besides Skype and Spotify, unfortunately there just haven't really been very many mainstream start ups coming out of Europe.

Also, I'm not sure what Alan Turing has to do with Sinclair and Amstrad failing and Dell being successful. From what I understand of the early development of the computer, much more work was done in Boston, NY, and the Valley than in the UK.