Each Country has its own particular codes.
I use rotary change over switches with a centre position as OFF. So we break to a positive OFF then we make.
All my switches are 2 pole minimum as the neutral and the positive are switched.
Earthing is difficult as each country uses differing techniques. Here in France we still use a 1.5m copper rod banged in the ground at each Consumer/RCD distribution enclosure unit.
I have many buildings here with each having there own consumer units so each is earthed independently and each has its own changeover switch.
1. photo show a installed Kraus & Naimer 90 amp 240vac change over switch.
2. Rotary Switch Change over connections.
3. Assorted Kraus & Naimer change over switches. The DIN RAIL MOUNTED one is 8inches/200mm long 8 pole, but you need to be Tarzan to turn that smallish rotary switch. (these are all second hand/used, but well tested and inspected.)
China makes change over switches, look at ebay, but please watch the quality.