Alright, thanks for further clarifications on all fronts!
I shall work towards diagnosing the source of the buzzing, either by taking the belt off and spinning each pulley by hand to try and see if one comes back with resistance.
I'll also be checking the power steering fluid for bubbles. I DO remember over the summer I think it was I had my car worked on and there was a LOT of power steering fluid. Like, so much so that taking off the cap and it seemed ready to overflow. I never got around to sucking some out with a turkey baster, but I'll probably do that if it's still full when I go to check it next time.
It might be a while before I'm able to work on the car as it's due to rain here soon and it's pretty cold, but I will try to report back my further findings when I do!