Hi I'm just going through the same process. You can do it in Manila at the British Embassy or at the Honourary Consul in Cebu.
The first thing you need to do is make sure you have your son's Filipino Birth Certificate on NSO Security Paper. Then you need to complete Birth Registration Form and the Declarations of Paternity/Maternity.
You need your wifes birth certificate on NSO paper and passport, and the same for you. All information is here
The exact information is here http://ukinthephilippines.fco.gov.uk...register-birth
After that you can apply for the British Passport, and because it's the first passport you can apply for it at the Embassy in Manila (takes about 4 - 8 weeks to receive it after that) .
You need this form http://centralcontent.fco.gov.uk/res...t-pdfs/form-c2
Details here http://ukinhongkong.fco.gov.uk/en/he...e-applications
