>I agree with AvocadoUnicorn, why would you spend thousands of dollars and possibly near 2 years of waiting for a GC that you will abandon cause you’ll leave as soon as you get it

Not only the cost for the application fees, adjustment of status fees etc, it's also the incidental stuff - getting the medical done in London (if OP's partner not in London, then it would mean a trip there plus cost of medical - which is NOT covered by NHS), plus any extra stuff that needs to be done like vaccinations (again, not covered under NHS), police record etc, trip to London for the K-1 interview itself and etc.

Overall the K-1 is an expensive, invasive (I don't know if it's every country, but mine expects *women only* to submit to an external genital check... for what reason, I don't know since that's not going to prove or disprove any public health risk) and long-winded procedure. If from an ESTA eligible country it's 99% of the time a far superior option to just marry and get a CR-1 which is only a little bit longer in terms of processing time. But again, if not planning on actually *living* in the US, a totally ridiculous and farcical waste of time and money and a delay for all the couples who DO want to live together in the US.