Cortana will hit the UK in the upcoming weeks. Marcus Ash, group program manager for Cortana, has confirmed that Cortana will arrive in the UK with a British Accent within the next 2 weeks. This region based specification is no surprise as we have seen Cortana singing in different languages.
Unfortunately, if you live in the UK and do not have WP8.1 Developer Preview, you will have to wait for the official 8.1 update.
