My 2 cents... You seem motivated enough to learn on your own. You also left off a key detail - where are you from, and what is the visa situation? 46K is not much to live off of in SF, and you could struggle to find a new job w/out a Visa.

All that said, you should consider some other things:

1) Do you want to live abroad? If you are young, this should dominate the decision. I am of the "Go abroad at all costs" camp, which means (if you're from London) take the job if you're in that camp too. If you're from the US, that's a case to stay in London.

2) Secondary ask what you want to do more, Fintech or Photo sharing. On the front end, your industry expertise will matter for the next job. Both are interesting areas.

3) Once you get into medium term thinking, how much you like your team matters an awful lot. It's not good short term (anyone can suck something up for 6-12 months) and not good long term (teams break up) but it's a good medium term consideration.

Good luck!