Rory,
May I suggest you review the UK in the Philippines website(British Embassy)
Check out the links down the right hand side, especially 'Help For British Nations', then 'Living In The Philippines'
If you scroll down the page you'll see plenty more info to help you.
You can find details of the British Consulate in Cebu by looking here
A couple of other useful links for you would be:-
Marriage and civil partnerships
and
Certificate of No Impediment
Happy searching !
