I wear a 10.5US Barrie. I can comfortably wear thick socks. They're a bit on the loose side with thin dress socks.
I've got a pair of 2298 in 9.5UK. They're a bit snug but work okay with thin socks.
Everyone's feet are different tho so YMMV.
You say you've got a high instep. Mine is sort of low but then it's kind of wide across the ball.