I used to work for a firm where the radio was a sore point. It was settled that we would listen to radio 1 in the morning and radio 2 in the afternoon. After a while the directors noticed that morning production was significantly higher than afternoon production.
I like listening to Radio 4 but not when I'm in the workshop, you see the problem is that I find myself putting off the next peice of machining because otherwise I won't be able to hear what is being said, with music it doesn't matter so much
I'm a radio 4 man as well. The only time I turn the dial is when the afternoon play is by Checkov. That man makes paint drying seem exciting. I find importantly that when I'm concentrating it turns into background noise. Some of the music channels are just too obtrusive and others are too moreish you always want to stop and listen if something good comes on.