Posted: 14/09/2012 at 08:58
We had this problem in our old house. We took to regularly cutting shoots off at ground level if they came up through the grass, and making a hole in the middle of where we'd cut and putting weedkiller in it. Worked to a certain extent, but it was a nightmare. We were too chicken to speak to our neighbour, but I would say that's your best bet. Must be affecting their garden as well I would have thought!