Same problem here, on TV and laptop so across devices, been about 6 weeks now.
Some of the shows seem to have disappeared from my watchlist on their own but there are still about 5 that can't be removed.
My problem is when i add a tv show it then adds every other tv show related to it, for example i added criminal minds and it also added 2 other versions of the same programme.
This watchlist problem has been going on since mid december, how embarassing for now tv that 2 months later they are no further forward, absolutely shocking, how about sacking your inept IT staff and getting someone in who can do the job properly !!
I have had this issue for months using the PS3 app. I have been trying to remove 3 unavailable programs and every time nothing happens. It is totally annoying as prior to the last app update I didn't have this issue.