Criminal records check required?

Hi,
I am currently working in China on a Z. I'm a UK citizen. I want to change company in the near future however, a friend told me that there is a new rule that for transferring Z type from company to company that a criminal records check is required for UK citizens to transfer my current one or if you move city. Is this necessary and also do I need to go back to England to get it or I can do it by postal service?

Any information will be greatly appreciated.
Thanks