I think Series 5 is still shot in 1080i50.

At any rate, it's never been a problem for me, as I never watch them any higher than 720p anyway.

--edit--

Just looked into it, and I'm sort-of right, sort-of wrong.

All Doctor Who since Planet of the Dead in 2009 (this includes Series 5) was shot at 1080p25. They were then edited, and effects were added, at 1080i50, as 1080p25 is not part of the broadcast standard. As such, the fully-edited episodes are locked at 1080i50. The UK Blu-Rays are (I believe) 1080i50, as well.

The US broadcasts are standards-converted from 1080i50 to 1080i60 for broadcast and Blu-Ray release.