The comments regarding negotiating payment are correct. A 50% reduction is in order, plus you can simply tell them to get stuffed, come collect.
Also, if I recall correctly, I believe Brits abroad are basically insured -— they turn the bill over to the Brit health system and it acts as a psuedo-insurance company.
Next thing to check and see how you paid for the trip. When I use one card (used for this purpose — not otherwise a credit card fan) for travel -— any emergency medical while I am there is covered by an insurance program. This is a very common benefit on Gold/Platinum type cards.
Thanks for the tips, we will investigate....