Hi, I'm a UK citizen living and working in Brunei. Do I need a visa to visit PRC?

Yes, you need to apply for a L type in advance. It requires your passport, completed application form together with a recent passport photo, roundtrip air tickets and hotel booking in Guangzhou. It takes four working days to deal with your application normally. In your case, you might ask the embassy if you can apply via rush service. It takes one or two days. And you need to pay extra money for the rush service.