Anyway, it doesn't really mean that Serenity dethrones Star Wars as UK's favorite, but that the majority of people they surveyed liked Serenity more than SW. It is hard to get non biased statistics. If they really asked every single person in the UK, I am willing to bet there would be a lot of people who have seen Star Wars who would say "What is Serenity?" and very few who have seen Serenity but have no idea what Star Wars is.
If only The Matrix was not on that list, I would say the United Kingdom has some pretty good taste in Sci-fi.