You could always have a chat with Environmental Health. Some years ago we had trouble with some former neighbours who thought they would burn mattresses and other material at 2am, hoping that everyone was asleep hence wouldn't notice. Unfortunately for us, we noticed as it woke us up . We called EH who served an enforcement notice as they were producing lots of acrid black smoke. We never did find out what they were burning but the EH officers said it was not acceptable stuff and potentially poisonous. It pays to have some faith in the council,I have found them very good on this sort of thing however this was before some cutbacks meaning that they were only on duty at weekends.