I arrive in hong kong stay 2 days then go to china and depart to uk from china what China visa required?

I am travelling from the uk in August 2012 for a 22 day guided tour of China which includes arrving in Hong Kong spending a couple of days there before embarking on the China tour and departing back to the UK from Beijing....I am not sure what type of visa I need and the tour operator I am travelling with, cannot advice me!!
Many thanks for any advice.