Well don't be surprised if you don't get it, even if they think you're good, at the end of the day the Chinese will let you move on, they can be stubborn. The way they view things, these days, they are always confident to replace you even if the next bloke may not be as good as you are. They will often let you go and scrape by with a teacher down rather than pay you more.

I remember years ago I asked for an increase because I thought I was good and they wouldn't want to manage without me. I was stubborn, so were they, so I left and found another job. What a fool i was by the time i calculated how much the moving cost me I ended up much worse off even though the new position paid more. Still you can try but do your sums first, how much things could cost-hotels, travelling, visas, and don't be too proud to back down if it suits your pocket. It's often easier to get other compensating things from them-a better flat, better teaching hours, stuff like that.