do any of you lovely computer peeps know what i can do?

unless you have a qualification in electronics, take it to an apple reseller, I have an A level in electronics, and I wouldn't touch a power supply.

so buy a new one then?

With any luck, you might be able to get away with just a new power supply.

Messing with the voltage switch tends to be something you only do once, though. :)

You can replace it with a bog-standard ATX power supply, after snipping the white wire from the plug.