Hi RB46, welcome to the forum!
It could very well be that you don't need antidepressants, I was in London for 2 years and it nearly drove me out of my mind, it was like being in the desert surrounded by people, being completely invisible, being dead and looking at the world around you - probably I was being over-dramatic as I was 22, but the memories are quite vivid, and horrid, in spite of how much I loved that city and all it represented.
Just an example: after some years of living in a place where people would say "good day" to each other even if they didn't know each other, I was used to make eye contact with others on the street and at least smile - somewhere in London, it was a secondary street, this guy was walking on the same street side, and I was ready to make eye contact: he must have seen that coming, because he deliberately averted his eyes and turned his WHOLE FACE!, and his body on one side, to avoid any kind of connection (and allowing me free way, had I been a pickpocket).
That was London in my experience, and everyone I know there lives the most alienated lives, although they all do very cool things, jobs, interests, etc .
Now it is different, there are several awesome meet up groups about depression and loneliness in London, (one wonders why), check them out, probably a lot of other people feel the same way you do.
Anyway, what you write arose a lot of absurd memories, desperate loneliness does have a way to creep in during London life, before taking antidepressants it makes sense to check if something else is missing.
take good care!
