I am a british passport horder, do I need a visa to visit china or will i get a visa upon arrival?

You need to apply for a China visa in advance, it is hard for you to get a visa on arrival.

If you just visit Shenzhen for less than 5 days, visit Zhuhai for less than 3 days, Shantou for less than 3 days, it is possible for you to get a 5 days Shenzhen visa on arrival, 3 days Zhuhai visa on arrival and 3 days Shantou visa on arrival.