If the intent is to stay permanently, rip out anything 220 specific and replace with 110 based items. If they undersized the
wiring because 220v runs at 1/2 the amps, you may need to replace the
wiring.
If it's short term or you just want to sneak by, get yourself a 110v
battery charger of large amperage, and a 220v-50hz
inverter to cover your largest loads. Wire the
shore power inlet to the
battery charger and the inverter to your AC panel. You now have quality 220v-50hz
power. The problem you run into is every time something fails, you have to special order it so you get the version that runs on 220v-50hz
power.
(before someone says it, yes you can get away with some items using the wrong hz but generally not a great idea)