Hello Gerard,
I have lived and worked in China for 2 1/2 years. When I come to China they sent me a "letter of invitation" from the school/university where I was to be teaching.
It is my understanding that you will need to get a medical form sent to you and you need to have a doctor examine you and then bring the test results, including the x-ray, and go to the nearest Chinese Consulate in your area to apply for the Z Visa. The Z Visa is the only Viza you can work with in China. I am sure if you were to contact your own consulate in China (I use the Canadian Consulate in Guangzhou, Guangdong) and they are very helpful in telling you what you need to get into China or what you can do once you are here.
Good luck and enjoy China. It's wonderful!