However, despite this very authoritative (ahem!) advice a quick google search reveals that although it is still a combination pill, the dosage is different! They both contain ethinylestradiol and desogestrel but Marvelon has 30 micrograms and Mercilon has 20 micrograms.
Also, it just happens to cost about three times the price! I think I was paying just over 20rmb per box for Marvelon and this is over 60rmb per box. Gah!
Hong Kong website: http://www.mercilon.hk/