I just don't understand why you'd choose Joss Stone. I mean if you're going to rob and murder a famous person, surely you'd rob and kill someone more famous, no?
A "more famous" person would have more security, so it wouldn't make more sense.
Like the poster above said - it was never about her fame, it was about her money. Joss has MILLIONS of pounds. They probably thought she kept a load of cash in a hidden safe behind a photo.