As Pumpkins said, you need to make an appointment at your local registry office to apply for a CNI (Certificate of No Impediment). It will take 21 days to come through, then when you get to the Philippines, you go to the British Embassy in Manila and exchange it for the Philippine equivalent which is a certificate of Legal Capaciity to Marry.
When you have this you just go to the province where you intend to marry and apply for a marriage licence which usually takes 10 days and in some provinces the 10 days does not include weekends. Other things you will need to get the marriage licence are your Birth Certificate and if you have been divorced in the past, you will need your decree absolute.
Then, while your waiting for your marriage licence, you will probably have to attend a Pre-Marital Seminar along with your wife to be, although, as a foriegner, you can sometimes get around this by paying a small fee, which is just a bribe really.
If your new wife intends to apply for a visa right after the wedding, then it's best to come armed with all of the evidence she will need to submit her visa application. You will need 6 months wage slips, 6 months bank (current account) statements, savings account statements, a letter of sponsorship writen and signed by you, proof of adequate accomodation, mortgage statement or tenency agreement, evidence of relationship and a good quality scanned copy of your passport etc, etc.
Iain.
