Because I don't have a TV, I basically watch stuff when it's available on ITV player, iPlayer or Demand 5 (Channel 4 has yet to broadcast anything I can even remotely consider worth watching).
I will always watch Doctor Who, Call the Midwife, Waterloo Road, Doc Martin and Downton Abbey when they are on. Fortunately, they rarely overlap more than two at a time!
When I've got time off, like during a holiday week or a "reading week" like this one, where I've been set exactly 0 reading to do, I'll watch British crime dramas - things like The Bletchley Circle, Midsomer Murders, any Agatha Christie, Morse, Blue Murder, Scott and Bailey etc. For sheer mindless decompressing or entertainment while tackling mammoth piles of washing up I watch American crime dramas like NCIS or CSI.
For someone without a TV I guess I watch quite a lot of it, but it's the best way I've found of getting myself to cook, wash up or clean - it occupies my mind while I get on with various chores.