You are very brave but personally I wouldn't take the risk. Myself and a friend reproached a workman in my own road doing someones wall dangerously and by blocking the pavement and he threatened us with all sorts of things despite our having two kids in buggies with us. You could have incurred serious injury as doubtless these people dont really care what they are doing. I would really take their number and report it again to the Councillor. Also try Cllr John Russell as he is very helpful in these matters.