Just a re-check on the advice you already received.
As long as you have your UK Decree Absolute you'll be able to secure you UK CNI
With the UK CNI you'll be able to exchange for the local Philippine CNI at the British Embassy.
So far so good.
However..... be cautious of a potential 'banana skin' in line with that intimated by you and additionally mentioned by sars above
Many 'authorities' responsible for issuing a wedding licence have started to request the CENOMAR for the foreign party.
Please do get your fiancee to :-
1. Just for completeness check your CENOMAR for correctness
2. Check with the authority where you'll be getting the marriage licence if they will demand your CENOMAR
In order to minimise any risks relating to the issue of your Marriage Certificate please see this forum thread from sars -
Advance Endorsement Birth ,Marriage and Death Certificate
Sorry if nothing new, just trying to help