travelling to hong kong to guangzhou back to hong kong then to shanghai. what visa do i require?

You need a double entry visa to China. Hong Kong applies different exit and enter controls, in China visa area, Hong Kong is regarded as a foreign country.

1st entry: Hong Kong to Guangzhou
2nd entry: Hong Kong to Shanghai

thanks for your reply.

while in shanghai we are planning a trip to beijing, guess as in china and travelling to china a double entry visa is still good

Yes, a double-entry visa is OK for you to travel from Hong Kong to Guangzhou and Hong Kong to Shanghai then Beijing.

now i know which visa to get anyone know the best way to guangzhou from hong kong, i know they do trains and buses, but ive been looking at flights and they ar expensive over £100. the train is a cheaper option is the visa checkpoint easy enough to get through on the bus and train

If you are a stranger in Hong Kong, I recommend you travel by train, which depart from Hong Kong Hung Hom Railway station. Clear the customs ( go through visa check point) is easy and fast.
If you don't like travelling by bus, there are also buses available at Hong Kong Island or Kowloon, which is a little cheaper than traveling by train. But it's not easy to find the departure stations and it takes more time to clear customs.