I am pretty sure it's due to having made a total pig of himself on, er, budget foodstuffs at after-school club this evening, but he has upchucked 4 times now: is there anything I can give him? He is also shivery, feverish and miserable poor little sod.
Keep him warm - can you sleep with him (with towels from the laundry basket under him and on the pillow)?, bucket by the bed, and water nearby if he wants a drink? But only give him sips of water. No food until tomorrow evening at the earliest. You can't give him medicine for a stomach bug.
There isn't much you can do, other than be a soothing presence.
Strong mint sweets (or toothpaste) will help minimise the horrid taste, it's probably something that he's just got to get out of his system. You'll need to check signs of dehydration in the morning, and get water down him (small sips, frequently). If you become worried about temperature, or if he becomes unusually drowsy (admittedly difficult to tell in the middle of the night) or seems to be in pain, ring NHS Direct or your OOH doctor for advice.
Oh don't worry, it won't wipe out the whole of half term. I bet he is feeling 100% better by this time tomorrow (just make sure you remember to take care of yourself). Vomiting bugs are usually pretty short-lived, so long as you starve the virus and don't re-introduce foods too quickly. And when you do: no dairy, fat or protein. Carbs all the way for a day or so.