Transit through Beijing and Hong Kong

Hi
I am planning a journey to China and Hong Kong and want to know if the following is valid with 5 day visas or will I need a full visa

Trip 1. London to Beijing. 5 day Visa. Then onward to Hong Kong

Trip 2. Hong Kong to Shenzhen. 5 day Visa then either Shenzhen to London. Or back to Hong Kong to fly to London


Thanks for any help

Andrew