With all the latest changes at the China visa embassy in London and Manchester, please note that special requirement is made for every China visa application. If visiting friends in China that are on a British passport, but are employed in China or have been seconded then you will need to have supporting China visa documentation. As well as providing the China visa application form, a passport size photograph, you will also have to provide a flight itinerary in and out of the country, along with proof of the person you are visiting. The person you are visiting will need to issue a letter of invitation and a scanned copy of their passport page and their china visa that was issued to them upon application.
Furthermore if you applying for a china visa as you are visiting friends and relatives that are natives of China, then you will need a letter of invitation from them, and if you can also provide a scanned copy of their passport page, then that would totally suffice in obtaining your China visa.
If you are applying on a china visa for business, then you will need to have the company you are visiting in China to approach their local government authority and have them issue you with a government authorisation form for the issuance of your China visa.
The application process for obtaining your China visa has become quite rigid in light of the upcoming games and Tibet issues. Fingers crossed that these rules for the China visa are relaxed after the Olympic Games.