Fans on with ign isn't standard, someone has modified it.
Had you done anything before the overheating? Quite a few people do stuff then don't say what the've done....:doh:
Was the water level ok in the bottle and rad?
It could be the thermostat, easiest way to test is to remove it and place it in almost boiling water and it should open fully.
it could be the head gasket, easiest way to check that is to get a
block test kit
you might get it cheaper elsewhere, this was the first one i googled.