I can't state for sure what is the legal status of UKNova. However, they have worked with copyright holders to ensure that they are not infringing. Most of the content is free to air British TV shows, that in many cases can be downloaded for free from within the UK. UKNova helps make this content available outside the country.

Their policy is to take down any content that is available commercially. IE: once the box set comes out, you can no longer share it. Other specific content cannot be shared even if there is no non-commercial source. It is easy to get banned from the service, so users are very compliant.

There are a lot of expatriate Brits who will miss the service, not to mention fans of British TV everywhere.