They never used to. I was watching the Vicar of Dibley episode, the one where she gets married. They cut a whole scene out, and then bleeped over the words such as Prick and Shag, yet left Fuck in.
It was shown after 9pm, yet the same episode was shown a few weeks ago on the BBC and they left all the words, plus the cut scene. Although, now I think about it, I do realisewhy they cut the clip they did.
I've noticed it on one or 2 other shows as well that go out after 9pm, they bleep out certain words, yet leave others in.