Hey, I recently received the offer from UCL, so the least I can do is offer my timeline for you.
I went to sit the online test on 12th January.
I got Invited to interview on the 27th February, and my actual interview was on the 6th March (almost two months later!).
Then i got my offer on the 18th March.
My predicted: AAB
Honestly, i feel it also depends on how you felt the interview went, because i honestly didn't think mine went all that well, they asked weird questions which i genuinely couldn't prepare for. But i also had gained experience from doing previous interviews, since receiving those offers made me somewhat more confident in my abilities to answer and may have been what pushed me over the line.
I'm sure you smashed it anyway, don't stress too hard since as you can see they love to take their time, and i hope this somewhat helped.