Yes wot, I'm another one - seems as if we're all at it! I talk to myself when I'm annoyed with myself, something along the lines of, "Oh for Heaven's sake, Indi, if you'd started this earlier you wouldn't have to rush - you've only got yourself to blame!" And then I'll answer with "I know, just shut up, I haven't got time to talk now." Only when I'm in the house on my own, of course 
And I have the 'practice' conversations too, tanith. I remember once walking back to the office from my lunch break and the security officer was standing chuckling at me. "What?" I said. "That was quite a conversation you were having with nobody!" he said. I didn't even realise I'd been moving my lips - apparently I'd been quite animated. Oh dear 