I need shopping tips!!

Yesterday I booked flight tickets for myself, dad and my little sister to go to London, yay, we're gonna visit my brother, who I miss a lot! and look around London, aside from meeting my brother I'm so excited about going shopping, I'm not gonna go nuts, but I want to visit all these amazing shops we don't have in Sweden, for example these above?
But I need some tips though.
Maybe I've missed a "must visit" shop, let me know...like, any other shops that are amazing for plus size women?
My brother, I and my sister are all fashion freaks, and love shopping so...this is gonna be a blast!
Can't wait to go!
London calling!