Guys, this is happening quite a lot at the moment - happened to me yesterday too. My problem was related to a build up of salt and some corrosion on the top part of the opening mechanism. When you lifted the tab to open the bonnet it was not moving the catch enough - so got some WD40 on it, pressed tab and moved catch to left with screwdriver - did the trick. I'd encourage everyone to check their mechanisms after all this crappy weather as it is easy to prevent.