The movie takes place in the UK and starts with the aliens already having Earth under control, as the father of the main character goes out with a baseball bat seemingly gone crazy. The alien robot tells him he has 20 seconds to return to the house and he's vaporized. Then his children run out and the alien again tells them to return, until another human comes out, gives it some sort of code that makes it stand down.
Then later, the main characters try to use a car battery to start a PS3, which shocks one and disables their ear tag, making them essentially invisible to any sort of tracking device. They go out for a bit until they see it turn on and run back inside. After some stuff I can't remember, they stumble upon some ex-military personnel, who say that the aliens controlled the computers in modern fighter jets, and were forced to use spitfires from WW2 (the one shown is a double canopy.) Later they use it to fight, and the aliens leave (I can't remember it.) Then the guy from the beginning is told he has 20 seconds to return, while he's in the British countryside.