It wouldn't be unusual for people wanted by the US for various matters living in Europe to avoid the UK. Roman Polanski, for example, was able to testify over video-link when bringing a libel proceeding in the UK, on the basis that he was quite likely to be arrested and extradited if he was to appear in person.

Clearly Roman Polanski also believed Sweden less likely to extradite him than the UK, since he has actually visited the former (where they did arrest him, but then released him without charge back to France).