Vauxhall Corsa engine, interior lights, ignition lights etc suddenly stopped working

Not long had the car, obviously had been abused a bit and has a dodgy stereo set up. I removed the stereo, all fine. Next day, took kids to school, car started fine, 1mile up hill, engine, dash lights, ignition just gave up. Still have headlights but nothing from turning the key. Must be a fuse/dodgy wire or something from the crappy radio but I dunno where to start looking in the pi**ing rain with 2 grumpy kids in the middle of nowhere in Wales!! Any advice welcomed before ride the next passing sheep off into the sunset.....