Does anyone remember when Kev Red first got his gutter vac? The posts were on his UK cleaning forum which he has since shut down, but the story was that he got a prototype (or maybe one of the first of a new model) that was rushed out to him,... but when it arrived there were issues with the way it was wired that he said made it highly dangerous apparently!
It was repaired rapidly,.. but mistakes can be made in the factory, and mixing this possibility + 240V + wet weather is just crazy.
110V all the way IMO,.. just get a big transformer for when you do domestics, simples!
The ultimate solution though would be a petrol/diesel powered machine. Nothing on the market at the moment is even nearly suitable though, a new unit would have to designed and built from scratch.