at bink!
Jako-o is here. They are very good for basics, though their 'designed' collections are more variable.
9 is a difficult age, tbh -- not quite big enough for small adult ranges, but too big for much of the nicer kids' stuff.
We've had success with most of the ones mentioned above: H&M individual pieces are nice; GAP ditto; Vertbaudet, DPAM, a few Boden bits, also Animal, Joe Browns, Matalan, M&S, even Peacocks sometimes. And Oxfam.
Also Petit Bateau do nice stuff in larger sizes these days, but ££.
I think you have to just have a semi-permanent eye out for reasonable gear and stock up when you find it.