I checked into Maplin and found there was one very nearby, and it had moveable pin chargers in stock. We have a chain of stores in Canada almost identical to Maplin called "The Source" -- I had not known Maplin was a similar store, or I might have checked it earlier. Anyhow, it was too convenient to grab that charger, not having to bother with click&collect. I got the USB powered one... which saves me from ending up with a UK plug I'd need an adapter for back home. May charge slower, but that's okay. It seems to be working fine.
So that's how this story ended, for anyone interested. Thanks again for all the suggestions and help.
Of course everyone knows this, but it never hurts to remind: always double check you have your charger when you leave home! And make sure all your spare batteries are charged before a long trip too!
(The stupid thing in my case was that i got the charger out of my bag just to charge a spare shortly before I left... leaving the spare and the charger behind.)