That's funny, from the OP and many others I heard the "it gets good and bang, it's gone" and from someone else, the "recycling of actors" My advice would be to stay the hell away from the BBC!! LOL
They LOVE cancelling shows the moment they start getting really good. The one exception being Doctor Who. Of course, since they can always point out The Doctor, they put everything else to the ax way too soon. Torchwood, Whitechapel, Primeval and the list goes on... three seasons of maybe 6 episodes and poof! gone.
And recycling of actors??? There's a scene in "Secret Diary of a Call Girl" where Billie Piper, (Rose Tyler) is having sex with the 11th Doctor (Matt Smith) and who should call her but the 10th doctor (David Tennant) calls her on the phone! Crazy.