My Phone has died

Had my phone on charge overnight the same as I always do. This morning it would not come on and appears to be dead. One strange thing though there is a small white dot of a light which flashes periodically in the top left corner of the screen. Tried charging further on a different socket, tried turning on/off but can’t tell if it is on or off now. Phone has been working ok until this morning. As far as I’m aware I haven’t done anything silly with downloads or applications. Any ideas?