Thanks everyone!

I consulted the internet about legal position. Both lawyers and local government authorities had plenty of advice. Same message on all, anti harassment court order. At least 2 incidents needed but applies to physical abuse, verbal abuse, harassment, actions that cause physical or emotional distress, etc etc.

Looks like they've gone on holiday, so will get some peace for about a week at least. Hoping owner comes round to cut grass, then I can talk to him. Shame the girl wasn't here this afternoon when I was talking to another neighbour's daughter (4). Can have a far more intelligent conversation with her!!

Spent pleasant hour in garden earlier tidying up without fear of being watched