What fuse do you need to run a 200 watt bulb with 230V?

The formula you are looking for is Amps = Watts divided by Volts. Once you find the amperage you can decide as to the size of a fuse you should use. Remember that fusing protects the conductors of the circuit and not the load of the circuit. A #14 wire is rated at 15 amps and can legally be loaded only to 12 amps.