I think it's bradford, east London, surprisingly the apartments there are really nice and for a fair price. The stadium he mentioned in the video I think is the olympic one or something?
for a 3 bedroom apartment (not a penthouse) is about 700-800 a week at most expensive, per person that's £233. I don't know who if anyone's sharing with him, but that's a family sized sweet apartment.
assuming its 700 a week (honestly there are 700 ones that are MUCH nicer, but not as high up)
that's 35k a year just on rent, let's assume 45k a year just for the sake of comfort.
I think considering he's worked at it for 4 years that's a cracking example of progress for a 21 year old.
props to KSI.