Hi RuBiX,
I think it might help if you could do some further research on the benefits of dual nationality.
Technically it has nothing at all to do with passports.
In principle, after taking the oath for British Citizenship you already lost Philippine citizenship.
In order to re-acquire the Philippine citizenship you would need to visit the Philippine Embassy to take the oath of allegience and receive your certificate of Philippine Citizenship.
The most important thing is that you would retain all legal benefits of being a Philippine citizen. Such as continued ownership of assets in the Philippines (land, property, bank accounts etc)
You certainly do not need to have a Philippine passport to prove citizenship. That is done by the certificate given by the Embassy. If you travel to Philippines with your spouse then BB privileges are still available when submitting marriage cert and Phils Naturalisation certificate.
My wife still did not apply a Philippines passport although she is dual citizen.
There are plenty of sound legal reasons to maintain your citizenship.