Thank you for your replies. I was going to contact local councillors but wanted to see if i could sort it out by contacting the council first. I know how the council must feel when the place is defaced within weeks of an area being cleaned up but to have to live beside it is even worse. My wife is ashamed to have visitors so we have to go and visit them instead! Needless to say the graffiti only appears in the morning after the night before, we never see anyone actually doing the deed. Futher down the road the council solved the problem by planting shrubs all along which eventually grew to cover the walls, but that did take a few years.
Thank you again for your interest.