thanks to all the hints and suggestions I received from everyone under my previous post
Despite my fears that ds2 would go ballistic that he couldn't have a drink after the 6am cut off point - it all came to nothing.
I woke him at 5 o'clock - he had two drinks and slept all the way to the hospital. St George's (Tooting) were amazingly efficient and within 30 mins of our arrival we were seeing the anaethetist. She put Matthew to sleep with some gas, so there was no faff trying to find a vein.
He was back an hour later. He was grumpy and fretful when he first woke, but within an hour was much more like his normal self. We were out of the hospital by 10.30am
He seemed to sail through the whole thing and I was very proud of him.
Now its just the wait for the results ....
Good Luck Mulsey and everyone else who have forthcoming scans under GA. It was nowhere near as bad as I thought it was going to be