"I am a Filipino working in London. My fiance is an American and he wants to apply for the K1 fiancee visa while I'm in the UK, is that possible? What's the process to apply from a country other than my home country?"
This is a very common situation, especially for a lot of our customers from the Philippines, and it’s not a problem at all. We’ve processed hundreds if not thousands of cases or petitions just like yours. The primary requirement is that you have to be a lawful permanent resident in that country (the UK in your case). Most Filipinos have a work visa in that particular country. But if you don’t have legal status in the country that you’re currently living in, this might complicate your case. If you’re residing legally in the UK when you file, you will likely attend the interview in London. In the case of a K1, you’ll schedule your own interview and your medical exam, whereas, on a spousal visa, the National Visa Center would do that. Everything else will follow a similar process, only it will be in London instead of Manila.
If you do change locations, make sure that you change your address immediately. You can do that online, or you can also do it when you’re filling out the DS-160 visa application. If you move back to the Philippines, you’d have to submit a request to transfer a case and this can be very time-consuming and can typically take between two and three months.