6 Music for me, it's consistently good in my opinion, not as good as it was, but still the best. Mary Anne Hobbs does my head in with her ambient techno shite sometimes, it's like she took some acid in 1989 and never came down. The Huey Morgan and Don Letts shows are the standouts.
If I'm stuck in a van at work with no DAB, it used to be Radio 2...