Apollo, Moelis and GS internships, UK and abroad

Hey guys, so I'm starting at a target university in the UK this autumn and am new to WSO.

I'm interested in PE and PWM for the firms titled above. I've seen a lot regarding how hellish it is to work for Apollo in general let alone in their LA office and although it sounds like hell i do want the experience of doing a summer internship there to see if I could hack it.
Really just here to ask everyone if they could impart some career advice for someone who is just starting out and is looking to get ahead if possible.

Any resource recommendations that would prove useful in helping to prep for PE, PWM and IB interviews would be fantastic but also any further insight and advice about how to avoid basic mistakes and navigate the process as someone looking to potentially go outside of London for experience.

Thanks in advance.