Okay, so this morning a mini digger turned up and he's been excavating the front garden area. So far he hasn't dropped the kerb himself. He may not if he's going to be parking his truck there as it probably won't mind the kerb.
Although he isn't happy with what's going on, their next door neighbour (our next-door neighbour) has decided it isn't worth getting into any further arguments with the guy and will just ignore him. After all, they live right next to each other. One of the other residents on the green however has phoned the council and after the conversation, is also planning on writing to them.
A washing machine into a storm drain is putting foul water into a surface water system. That is indeed wrong. Grey water from washing/bathing/laundry can be collected for re-use i.e. watering your garden. This was the original plan, but I think he must have realised that a single water butt wouldn't have sufficient long-term capacity. Instead he built a soakaway/small hole filled with hardcore/rubble. If it was just rainwater it'd be fine as there is no requirement to discharge rainwater into a drain. However, as there is a basin outlet, then it should be either collected or diverted into the drain. I don't think it matters that the basin "isn't used".