All the symptoms could be explained by a draining battery, and the key is to understand why the battery is draining.
If the car is still on it's original battery it could simply be that the battery itself is no longer holding charge properly, for a 2007 car that would make it ~ 10 years old which depending on the use it's experienced during it's life could mean it's simply reaching end of life. A decent garage should be able to test the battery for you or you could rule it out by replacing it since they are unlikely to be massively expensive for something like a Zafira
If the battery itself is fine then there could well be something draining it - these can be an utter nightmare to track down as a it can be anything from a short in the wiring loom to a malfunctioning bit of electronics to a poor grounding point. Check the usual suspects out first - make sure you haven't knocked any of the interior lights to an "always on" setting, if your 12v sockets are "always live" make sure nothing has been left plugged in, that sort of thing.