Thanks for the answers to my questions guys.
It just makes me realise just how clever mankind has got to be able to contain and work with these extreems (and to make them spin in those conditions) I could go on asking questions on the subject for ever, but I think people would get bored with me.
Is there any laymans guide to this technology kicking around - a sort of 'Engine design for dummys' (as per the series more common in my IT world) ?