ok,have stripped boot out to look for anything that could knock and found nothing likely,so is it the bumper???.no its not it was a wheel bearing all the time!!!!!jacked car up to check and bearing had a tiny bit of fore and aft play.so changed it and hey presto the knocking has gone :).while doing that noticed the bush at wheel end of torsion bar is worn,ok £10 worth of bush ,half an hour and sorted!oh no,can,t get the bush only whole new arm and knuckle assembly approx. £380 .REALLY? what a rip off,