At this point in time; searching for an answer to your particular situation using Facebook is the least optimal option. Contact a Visa Processing service OR go to immigration and ask them what your options are and go from there. Good Luck.
I've tried every remedy suggested and still get stuck in the "do loop". Can't seem to break the curse. Other more astute (or lucky) retirees have had success, but not I. Keep trying if you have the time. Or, accept your plight in life as I have and simply do your "check-in" in person, where you can put your Mk 1 Mod 0 eyeball on the stamp /paper proving you fulfilled your obligation. Some of the "on line" systems seem about as reliable as gas-station sushi.
Sounds like limited choice even though you don't want to go back to UK, seems you would best be served if you simply accepted that fact and worked the details while there is still time.