(Thanks to Nabu San for link)
http://sarahjanetv.blogspot.com/2009/09/and-we-have-trailer.html
Also, the BBC Press Office have posted a fab 30-second teaser of Prisoner of the Judoon on its website:
http://www.bbc.co.uk/pressoffice/pressreleases/stories/2009/09_september/28/cbbc.shtml#item_15
In the above link (press office) click on the SJA photo on the right hand side to view trailer.