It can be done two different ways I believe. The simple (ish) way is to use an inverter designed to do the switching internally (my friend has one but I can't recall the make) and the complicated way is to use a switch designed for the job plus relays to disable any battery chargers.
Both need some electrical competence as there are several serious danger points - like you must isolate the 240v pins that you plug into an external power source!
I'm with Drover, I much prefer the good old separate inverter power socket(s) so I can see what is plugged in and for how long
Thanks guys for your replies, appreciate it.
Took a while to figure how they worked everything. And that.s the way I figured.
I have removed , the Setec unit, created three circuits
(1) Mains - (Double pole rotary switch) (2) inverter
This allows ALL existing power points to be used on (1) mains or when switched (2) on inverter.
Without possibility of have both active at the same time EITHER ONE OR THE OTHER
(3) 12v is split fused to "Lights" , "Fridge", "aux"
Battery js charged by the solar Thanking you all