British passport are exempted from visa to Hong Kong for 180 days. so you only need to apply visas for Mainland China. And it can be processed in Doha if you live there. Basic requirements are original passport, application form for China, photo. In additon, for tourists, you shall evidence your financial capability of covering the travelling expenses in China, and when necessary, provide the air, train or ship tickets to the heading country/region after leaving China.