Having recently married in Davao (it will be 3 months tomorrow) I hope the experience of my wife and I can help.
Firstly, Ian I am sorry to read of your loss and wish you every success with your new lady - you are certainly due some good fortune.
Now to answer Arthur's points; when you land in Manila get to the British Embassy ASAP with your CNI, there they will convert it to one acceptable to the PI authorities. There will not be any initial interview at this stage but PLEASE do get your documentation correct first of all. While we were waiting our turn we saw 2 seemingly intelligent people distraught because there was some error in their paperwork and therefore they were refused the CNI. You need the correct fee too as they are reluctant to give change.
Once we were married (civil ceremony) it took several days just to get the basic marriage cert from the Courts of Justice to City Hall. Once my wife had this (by now I was back in England) she got the staff at CH to electronically send the info to the NSO. She was advised that it would take about 1 month to come through. This is the 'quick' method. So much for the electronic age!!
After about a few days she went to the NSO in Davao and asked if they could really speed up the process. They gave her a date when they thought it would be available (about 3 and a half weeks after it was submitted). On the date specified she went to collect it and fortunately it was there.
She had already pre-booked the meeting at the VFS (assuming the NSO cert would be ready) and had her meeting 1 month and 1 day after our marriage had taken place. We are now waiting for the Spouse Visa to arrive.
Two more points to consider. You will need luck (and possibly more) on your side if you are going to get everything processed from CNI at the Embassy through to getting married in the 3 weeks. Once you have your CNI you need to go to City Hall in Davao (it closes at 5pm and allow up to 1 hour for them to process the paperwork). They will then display your marriage application for 10 clear days (including weekends) before you can collect your license to marry.
Now here's the second point which you will not find this on any of the official sites. For a civil ceremony you need to get a Judge to marry you (simple enough) but in Davao, and possibly every other city, the way they allocate a Judge is a lottery.
On Thursdays at noon they put the names of everyone who has applied to get married by civil ceremony into a raffle. The names are then drawn and allocated to the Judges. You then have to make a representation to the Judge for a date and time for your wedding at his convenience.
This can add days to the length of your stay. It is also a nightmare to plan for your wedding celebrations as you cannot arrange anything until you know that date.
My wife and I had good fortune (and friends in the right places) that enabled us to know in advance which Judge would marry us and what date and time (welcome to the Philippines!!!). Had we not been in that position the 3 weeks that I had planned on staying would not have been long enough and I would have returned to the UK a VERY disappointed man. As it was we had a few hours as husband and wife before I flew back to Manila.
I really hope that this helps anyone in the position that my wife and I found ourselves in. I certainly wish we'd known in advance as we could have worked the flights slightly better to suit the 'Thursday Raffle’.
Andy