I've got a similar problem but mine manifests itself as pauses when some sounds just won't come out for a while, rather than B-B-B's. I find it bl**dy annoying but I don't know what ATC think.
It's a strange affliction. I give tolerable business presentations to large international audiences. I've been instructing for years (aeros, tailwheel, multi, imc, gliding, etc) and it's not a problem. Many times I'm fine on the radio but for some unknown reason sometimes the voice just doesn't want to play.
On my recent IR renewal I was fine on the ground, but when I called Approach the voice decided it wasn't going to work and the stress levels from not being able to speak fluently nearly made me blow the test.
The Cherbourg tower controller told me that French pilots can't get a PPL if they have a stammer, but that sounds a bit unlikely.
This seeems like a good opportunity to say hello to the good boys and girls at Solent and Bournemouth and to thank them for giving so freely of their air time
