You will need a Certificate of No Impediment (CNI) which you get from your local registry office (after you apply for this it takes 21 days to be released). To apply for this you will need to know lots of details about your intended like her full name, address, DOB, her parents full names etc and you will also need to know details of the intended wedding date and venue.
She will need to get a Certificate of No Marriage (CENOMAR) and she will be the one who makes the visa application. These days this is usually done by filling in an application online and printing it off. The visa application fee must be paid into one of the British Embassy's designated Philippine banks. Then she must make an appointment at VFS in Manila
http://www.vfs-uk-ph.com/ .
When you go there to get married you will need to exchange your CNI at the British Embassy in Manila for the local version. You will need to allow enough time to do this and then at least another 10 days for the waiting period for the marriage licence. When you apply for the marriage licence you will also need to bring with you both your birth certificate and your divorce decree absolute.