Jon,
Can you go back to GB and get treated ASAP if you agree to pay what you can when you can?

If so that might be your best option and I believe not a lot different than what happens with many uninsured and under-insured here in the States.

I don't know what my treatment cost, since it has been paid by my medical insurance, but I have heard amounts on these forums of upwards of $150K. They might bill less for an uninsured person and/or in the UK.

Looking at your options, I would think incurring the debt is worth it and if you look at it from another perspective, over a ~35 year career, in present day dollars, I have spent nearly $200K for medical insurance!

I few year back, remember how I was always bitching about the medical insurance costing more than the lease on my BMW!