How to become a post MBA associate in London?

As per title, I'm trying to understand what the IB job market looks like for MBA grads in London. I understand that there are only a few banks that hire MBA summer associates (GS, Citi, Bofa - anything else?), but what if you don't get a FT offer and just end up with summer associate work experience without anything else lined up, is it a possible for such people to successfully apply for open associate roles at other banks if there is a role opened? By successful I mean getting a role at the end. 

I'm confused how it all works, because I went through many currently available associate job postings and roughly 99% of them require IB experience at the analyst level so such offers are great for IB analyst but definitely not suitable for someone with no IB experience prior to MBA. But if let's say someone does a summer associate internship at GS, can they later apply for a FT asso position at another bank?

Can you please share any insights? Maybe some of you are involved into hiring post MBA associates?

I know that it's much better to do an MBA in the US/recruit there, so no need to tell me that, but I just want to understand how people willing to work in London should navigate the post MBA asso recruiting.