You have booked with the Embassy in May for your appointment to exchange your UK CNI? I did not think that was possible. You CNI is only valid for 3 months fron the date on it in the philippines even though it has an indefinite life span in the UK. Make sure from the date you applied for the CNI to the date of your wedding is less than 3 months. The Embassy can be quite picky. When i emailed the embassy i was told i could not apply for a date until i had all the required documents in hand.
I got a 59 day visa at the airport last May. It is very easy and straight forward, just ask for one and they will give you it for a small fee, no checks.
Hope all goes well.
