The guy you met was a creep who took advantage of you being new to the sex industry. There are dirtbags like this who do this kind of thing. Please don't think it was a vulnerability thing on your part, very few of us find ourselves in a position where we know who to speak to when we first start out. You don't have to 'audition' or 'interview' for people. What I will say though is that there's plenty of things I did when I first started out that if I knew then what I know now, I would have done totally differently. Don't be hard on yourself.
I have always been independent so couldn't point you in the direction of parlours, but I do know that there are escorts who offer no penetration and manage to do just fine. Without being crude, some men can't have penetrative sex for a variety of reasons and they are quite happy with oral etc. Even if you aren't comfortable with that, there are, I believe, people who offer massages with hand relief. My understanding is that there are women who also do this independently although I understand that this isn't an option for you (and I know how being a student in London can be particularly precarious with accommodation). My point is that it is doable, so please don't feel limited. Sex work is pretty multi faceted and you don't have to do things you don't feel comfortable with. I understand your reasons for explaining why you don't want to have penetrative sex but again, what I'm trying to say is it is your body, your boundaries, your rules. There are things I don't do within my work that other providers do. Men who want those things should and would go to other providers - happy days, problem solved.
This is the sex industry though - there is sex involved, even if it isn't penetrative sex.
I hope you get some help re London.