I would strongly suggest that you check the UK Border Agency website. This contains all the information you need concerning Naturalisation.
Also the AN form is there and you can download it along with all the guidance notes.
I think the fee is still GBP735 but I can't remember if this includes the Citizenship ceremony fee.
Important thing is to really check out their website as if you do not comply you will not get any refund if your documents or qualifying status is incorrect.

First important point is that you must have passed Life in the UK test. When you have done this you will receive a certificate. The test costs about GBP35 I think. If you do not pass first time you can take it again and again until you pass. You cannot apply for citizenship without this.

When your application is approved you need to attend the Citizenship Ceremony
where you will receive your naturalisation certificate.

Once you have this certificate you are able to apply for a British Passport (If you want)
The British Passport also has to be paid for and you may be requested to attend an interview.(My wife was requested to but it was not a big deal)
Also you can fix up an appointment at the Philippine Embassy for your Oath Taking to re-aquire your Philippine Citizenship (Dual Nationality). Again you will be presented with your Certificate.

You should check out this website also to be sure you understand the regulations and process. My wife had a British Passport and Philippine passport, when she applied for her Dual Nationality they cancelled her existing Phil passport and asked her to apply for another!! She did not do this immediately. When we recently visited Philippines she presented her British Passport, Phil Nationality Certicate, Marriage cert and Birth Cert to immigration in order to have Balikbayan stamp for me.

Terpe