Dulwich fox yes I did see that question on the forms i filled in for Soicitors pack, at the time din't know we had it, but will change it accordingly now, as no interest in covering it up. It was the estate agent who is marketing our house who pointed it out to me and they seem reasonably professional enough to not want to cover it all up either. Our task now is to get network rail to put in writing that they are treating/managing the knotweed. Once we have that in writing it should help things move along ok.