Paxman
Does anyone in the UK powerwash live 500,000 volt insulators using a helicopter?
Nope because: -
1/ our maximum transmission voltage is 400,000 volts
But more seriously
2/ the only live line operations approved, by any means, in the UK are at up to 11,000 volts from insulated "cherry pickers"
Helicopters are used for line patrol and load lifting in dead line situations