Ive just tried the plug method, guess what, it worked !
The reverse polarity light went out.
I think I'll wire in a switch.
Also, is it ok to wire the switch directly from the inverter AC out terminals ?.
So just a simple switch on the AC out of the inverter that effectivly joins the N & E ?.
And if I was to make a "temporary" link with a wire placed across N&E on the inverter ac out to test if it extinguishes the the reverse polarity light ?