C+C 55 plate drivers door lock issue

Hello everyone, I was wondering if I can pick your collective brains please? SWMBO has a 55plate C+C essenza, and we are having an issue with the drivers door. More often than not, we can't open it from the outside. You can hear it unlock, and you can open it from inside the car, but from the outside, the handle just feels like it's still locked. When you lock it, it makes the famous farting sound, and has done so for a while, but didn't affect the opening of the door. I can't find a Haynes Manual on the C+C - would the doors on a 2 door micra be the same? Does anyone have any ideas on how to resolve this please? I'm no mechanic, but not bad with a spanner or 2, so will try to attempt most things myself.
Any tips or advice would be most gratefully received!

Thanks in advance,