I have been going to Jeju for years. It's a lovely independent salon with great staff who really know what they're doing and are always really lovely too. Total recommend this place.
The place is easy to find only a few minutes walk from the tube/bus station. I liked my haircut, just like the picture I told to the stylist. It was actually pretty packed during evening, but it was okay.
I have been going to Jeju Hair for the past 4 years and will never go anywhere else! Eunju is extremely professional, experienced, and reliable, so I know I will always get a good haircut even when I change styles. I always leave the salon happy.