Thankyou all for your replies, much appreciated and interesting.
I really have no choice but to slowly ease in if I get breathing difficulty again, as this is mentioned in Dr Fuhrman's book on fasting as one of the signs to indicate a fast should be terminated. I don;t know for sure but I find it hard to believe the body isn't able to do part-glycolosis and part-ketosis simultaneously, after all this would probably have occured naturally during our evolutionary past.
Anyway I will be sure to post if I get past day two. Hoping to start next week if work allows.