It would interesting to know if you could contact the National Statistics Office and collect your marriage certificate there instead. I take it when one reported their marriage in the Philippine Embassy-London, along with the self-addressed envelope, the marriage certificate will be sent to the address placed in the said envelope. I've just read through the PH Embassy site that it would take a month or two for the delivery of our NSO-authenticated marriage certificate.
My husband and I reported our marriage through the Consular Outreach Mission in Gloucester 2 weeks ago. We used a special delivery envelope so that we can track it.. I hope it will arrive soon.