If its not the ignition switch, its the ECU relay, £13 from the dealer. its not the fuel pump relay, people get confused as some cars have one of each and some share the same and its known as the fuel pump relay, the golf has one of each, and its the ECU relay that fails, this causes the fuel pump to cut out and loss of ignition, usually sticks when going from the off position to the on position, in bad cases it cuts while running. If it wont start, stick your hand up the fuse box and flick/tap the relay, If it clicks and pump primes, it will start, and there's your problem.
Otherwise, ignition switch will be the problem.