Blimey, the paranoia round here!
DoctorWho.tv is the official BBC Worldwide site for the series, mainly there for flogging merchandise.
I certainly wouldn't classifying enquiring about the authenticity of a website to be paranoia! That's something you should always do when obtaining information. Surely you don't believe everything you read on the Internet?
In this case, yes, it does appear to be a legit BBC Worldwide website.