Hi Nicola,
A colleague of mine has recently returned from a trip in China and advises that the equivalent of £30 a day in Chinese Yuen should be enough.
We'd recommend you take a bank card as well, just in case. Your tour manager will be able to help you find places to withdraw cash safely if needed.
There are currently 22 people booked on the main tour and 12 on the Hong Kong add-on for the 10th October departure.
thanks,
Jamie