During my 3 week stay in Tacloban back in 2004, I used a Natwest Maestro card, and it wouldn't work in any ATM. I remember calling Natwest and they claimed nothing was wrong, card not blocked, etc. Then I tried Metrobank customer services, and guess what, they blamed NatWest. So for 3 weeks, I couldn't access £000's in my Natwest account, luckily my credit card saved the day. I remember the Natwest card worked fine in Hong Kong, but as soon as arrived in Philippines it clammed up.
I'm with HSBC now, and I always inform them when I'm flying out to Philippines and Hong Kong, and I have never had a problem (yet).