There are a couple of great preview clips of John on 'The Making of Me' at the BBC.
Here:
http://news.bbc.co.uk/1/hi/programmes/7521689.stm There's a fantastic bit showing him speaking in his Glaswegian accent with his parents; and it's hilarious when he squeaks, "I'm straight!?!?"
And here:
http://news.bbc.co.uk/1/hi/programmes/7521776.stm