Visa Enquiry from a person in Ireland but currently staying in UK

I am a British Citizen visiting my daughter in England and temperarily staying with her as my home is in Ireland. I have an invetation letter from a company in China. I wish to apply for a one year multi trip one whilst in the uk as I have purchased a ticket to fly on 29/12. Can you tell me how long it will take as I will apply personaly and what if the fee. Many thanks.