We really enjoyed staying at Seoul 53. The owners are very friendly and helpful. Each day you get a free bottle of water and a basic breakfast of toast, bananas and tea/coffee. The rooms are simple but very nice and come with toiletries, slippers and towels (the towels are oddly small so you cannot wrap up, but they are fine to quickly dry off with). There is good wifi in the rooms, a couple of computers to use downstairs and a DIY washing machine on the roof. A very good place to stay and well-worth the price.
Nearby are several small convenience stores, a range of restaurants and other shops. The nearest metro station (Jong-no San(3)-ga) is just five minutes walk down the road, with three of the main lines passing through. Jongmyo Shrine is also nearby. Five minutes in the other direction is Changdeokgung palace. The direct bus link to the airport leaves from outside the palace too, so it is very convenient.
It is a little tricky to find, but not very very difficult - it is on a lane, off a sidestreet from the main road. When on the sidestreet, the lane is where building No. 53 should be if there wasn't a lane there!
We stayed at Seoul 53 twice during our time in Korea and if we come back this way then we will definitely head straight back to this hotel. Thanks for a great time!