Business Visa for UK citizen living and working in Vietnam

I am a UK citizen currently living and working in HCMC, Vietnam and have a temporary residence card. The UK Company I represent has an RO in Shanghai which has recently been placed under my charge, thus I will be required to travel frequently between HCMC and China to further develop our business there.
Please advise, the requirements for a 1 year Business F Visa, noting that we already have an established RO office in Shanghai, letters of invitation (if required) the price of the application in Vietnam, and can I apply for the Business F in HCMC.
Kind Regards
Mark A. Whorlow
Director DSA South East Asia