Rather short notice, sorry, but somebody told me there's an English-language Christmas mass at the Catholic church in Gwangju's Wolgwang-dong tomorrow, the 25th, at 3pm.
http://www.wolgwangenglish.org/wattawoman started a thread about
English-language services in Gwangju, and there's some info about other English-language services in Korea. Regarding the church in Wolgwang she says
The website includes the church's address and tells you exactly how to get there by bus. It includes a map you can give to the taxi driver. The church is near the World Cup Stadium. Take bus 16, 20, 47, 50, 74 or 77 and get off at the Yumju 4 way. Walk up the hill past Hwajeong Nam Elementary school.