Like what iain said its better that your fiance apply for his cni here in uk first then have it converted there in the philippines in the british embassy for a local one. It will only take 10 days (some including saturdays and sundays, others also the 10 working days really) depending upon the place your going to marry to get marriage license. After that you can get married anytime. I think you only need the 21 days requirement period of stay in the Philippines if the british cni was not done here in the uk in the first place. Its one of the requirements before the consul can give you the local cni. And marriage certificate i think sometimes takes so much time to be produced especially NSO in the philippines as well as the local registry takes so much time to process it. Hope this helps
