I'm a British citizen who is normally resident in the US and my health insurance through Premera (an individual plan, not a group plan or through my employer) is a very cushy plan with solid international coverage through Blue Cross / Blue Shield's "Blue Card" programme (provided by AXA, I believe).
As I'm no-longer considered a British resident (and neither pay any UK National Insurance contributions) I believe I'm not eligible for free-at-the-point-of-delivery healthcare, including emergency treatment; but the UK NHS accepts Blue Card insurance so I wouldn't be facing a crippling hospital bill if I were to be hit by a London double-decker bus tomorrow.
I'm currently visiting my parents in the UK and I'll be returning to the US in mid-January.
As it so happens, starting on 1st of January 2017, Premera has decided to eliminate my entire healthcare plan, and also raise insurance premiums by 25% on top of what I'm already paying for the next-closest plan. Among the regressive changes with the new plan is the removal of international health insurance. This is a problem: I'll be uninsured in the UK after midnight US Pacific time on New Years Day.
(This is likely due to the ACA's knock-on effects - but please make no political "thanks, Obama" comments).
So far from what I can tell travel insurance providers require you to buy coverage before you leave the country, sometimes as much as a week in advance.
What options do I have for buying insurance for a couple of weeks while I'm already out of the country?