Hi Ronan,
I got my no impediment to marriage certificate from my local registrars office in the Uk. This took 21 days. That is all the paperwork I brought with me to China. I took this to the British embassy in Beijing, who took this off me as well as 725 yuan and said " come back in the morning". They give you ALL the papers you require for a marriage in China , in both English and Chinese. You do not need anything else, nothing. We took the papers to the Gov office and were married the same day. No medical, no problems at all.
After you are married and your tourist visa is about to expire go with your wife to the Security office with your passport and red marriage book. Your wife will have to take her Id and home residency papers. You get a five month visa with unlimited extensions, for free. I know this because I was there yesterday. If your going to work, let your employer take care of the work visa, it's not your problem, it's there's
Don't sweat it !