For a resistive load if the voltage is higher then the current is higher and the wattage disapated at the element is higher.
If you have a rated wattage at 230 volts that means you can calculate the current at 230 volts.
If the actual voltage is 240 then the current will then be higher
Bernard ... I'm sorry but there's no other way of saying this ... The quote above is quite simply the biggest load of nonsense I have ever read by anyone posting on this forum.
Please produce formulaic evidence to support what you have said ... You can use the OP's P, V and I if you wish.
MW