I'm trying to find a mains double pole 15A change-over switch with an OFF position too - but no luck so far. Can get contactors to do it but want a manual c/o switch.
The only idea (yet to get checked) is to use the two-position switch that *some* showers have. (Not sure it they are 15 A *and* DP though). Anyone know if they are - before I buy one to find out :-) thanks