Well I finally got fed up with the noise and frustrated with not being able to find a solution so I took it to the local Toyota service centre. They confirmed that it was definitely on the left front but after checking all the steering and suspension, replaced a worn tie rod end, rotated wheels, drain and replace front diff oil, checked left CV, they have no idea what is causing it. Their thoughts are either wheel bearings (which I have already replaced) or CV shaft issue. I'm surprised that no one except Manxman has offered any ideas?