I wonder why it’s taken so long. But coming soon, in a new translation by Minsoo Kang, is The Story of Hong Gildong, “arguably the single most important work of classic Korean fiction,” according to the publishers, Penguin Classics. A release date of 7 July 2016 is mentioned, though Amazon UK is offering it on Kindle already. It was released in the States earlier this month, with a review in Shelf Awareness.
A 2008 graphic novel version by Anne Sibley O’Brien is also available from Amazon UK.