You actually both need a CENOMAR, they can both be applied for online at www.ecensus.com.ph . If your fiance pays for both locally and gets them both delivered to her house, thats the best option.
You need to apply for your CNI, you can do it at your local registry office (30 pounds i think), and then wait the 21 days, it's then valid for 3 months. When you get to the Philippines you goto the Embassu or consulate who will convert that to a local CNI. You the present that at the city hall to obtain a Marriage License, which takes a minimum of 10 days.
Normally it's all fairly straightforward, all the very best.