Thanks to all for your advice and responses. Jonathan had both an EHIC card (Sorry Debs, Not E111 as I said) and travel insurance. The Department of Health and Other Stuff have advised me that, as Debs said, I'd have a smaller bill for ambulance etc, the same as a French citizen and that they'd pursue this on my behalf so the position looks a little brighter.
Andy: I'll cover the rest with travel insurance.
Debs: Thanks for the advice - hope you're recovering sweetheart
Andy Z: Jonathan is still having scans and blood tests but it appears that his wobble was due to dehydration (let that be a lesson to us all - he simply hadn't drunk enough beer) but the tests have revealed a B12 deficiency and suspected pernicious amemia. His doctor has suggested an alternative diet of Monster Munch!
Big H: Having just dealt with a chicken pathia, onion bhaji, mushroom rice, poppadoms and pickles I'm letting the sieze cent soixante quattre brew the solids into a festering mass before expertly dropping it into a zip bag for delivery to those responsible.
(Apologies to those of a delicate constitution)
Thanks again friends