Hi Roman,
I have over the last few months worked hard in trying to get a 'real' answer from the UK's main Registra's office about the validity time of a UK CNI. I have asked the question as to 'when' the 3 months start 'from'
I was told when I got mine that the 3 months starts from the date of application, ie: the day you go to the registry office and pay your money. Others have been told that the 3 months start from the 22nd day, ie: the day the certificate is issued.
To this day, I have not been able to get a definitive answer, and this is from the 'top'..... they just cant decide.....
My answer to you is that if you arrange your CNI and your marriage within the 3 month period from date of 'application' you will be fine. When you go to the British Embassy in Manila to exchange your UK CNI for a local one, I think at this point you are safe. Although, I still recommend you arrange everything within the 3 months I have advised.
I hope that helps you a little, and my best wishes for your future together.
