I received some information from my uni about this and apparently some of it was wrong, acc to this board. And it still didn't answer all of my questions.
I'd like to know as much as I can now so I don't have to run around in London (as opposed to going flat hunting) and compete with other students to get my questions answered at the registrar's (?) office.
I'll be staying in temporary housing (with a distant relative) until I secure my own.
Fair enough
. You may be okay to open an account using the temporary address you will be living at to start with - you'd probably have to check with the bank branch you want to open the account with to see if that's okay.
I'm not sure if they will do it at your university, but at both of the ones I attended in the UK as well as the one in the US, they had special talks, presentations and workshops for all of the international students about how to open bank accounts and get all the other things sorted (including helping you look for somewhere to live).
The international/study abroad office will likely be reserving an entire week of their lives in order to help you and the other new students arrive and settle in - they should be happy to answer any questions or concerns you have about finding accommodation and getting your money sorted out. There may even be volunteer students who will walk with you to a bank and help you open the account so you don't have figure it all out on your own (I was a volunteer my final year of university - we met the students in the airport, drove them back to the university, took them on campus and city tours, helped them find houses and flats etc.).
Of course, there's no harm in trying to get your questions answered before you arrive, but to be honest, there are some things that you may not know for sure until you get to London (like whether you can use your temporary address to open a bank account).