Hi
I kept meaning to update this but time just keeps running away from me!
What worked in the end was a trip to the children's hospital in Aberdeen (emergency ferry followed by air ambulance) and being on a drip for 2 days. He was admitted with a blood sugar level of 2.1 and a ketone level of 3.4.
The drip sorted everything within hours and meant he didn't have to eat so his stomach got a rest. His body just couldn't cope with such a prolonged period of sickness (vomiting lasted 6 days).
Let's hope we don't have to go through it again for a very long while.
Annette