Channel 4 have put out a showreel of their up coming dramas. There looks to be some decent stuff there. Take a look here. [yt]http://www.youtube.com/watch?v=O-sy0-EYdNM[/yt]
The Merlin and Hunters trailers have been good for Beeb 1 too. Don't know if there's anywhere that they'll show outside the UK though.
[yt]http://www.youtube.com/watch?feature=player_embedded&v=WXDq_a0l4Zc[/yt] BBC One's showreel from a couple of months ago Made in the North reel [yt]http://www.youtube.com/watch?v=L8E0kO6AmE8&list=PLCED9757CB4C06FF6&index=2&feature=plpp_video[/yt]