[ttg4l]

Either that or a top mount bearing has gone and the noise is the rubber mount rotating and rubbing against the metal. Spray some light lubricant around the top mount on that side, if the noise goes away then it's that.

 

[ttg4l]

Ideally do both, but it's not necessary, so to speak. You'll need an alignment afterwards, so if it were my car I'd do both so the alignment can be done with fresh parts, and saves having to do another alignment if the other side fails soon after.

WD-40 is fine. No need to remove the bolt if there's enough space around the cap to spray into the gap (in that picture there's plenty of space if you have a straw on the can). Be liberal with spraying it so it actually goes around the rubber bush.

 

[ttg4l]

@ttg4l you were spot on, thanks.
I jacked up the front of the car, lifted the front sway bar a little, undid the screw and sprayed WD40.
Now all is quiet.
View attachment 53478

I'll do the outer tie rod ends and tie rod assembly at some stage.

Glad to hear you've found the source. It would mean ideally you'd get new top mounts and bearings at some point, but it's by no means urgent. I sprayed WD-40 on mine about 5 years ago and still haven't replaced them. I'll probably do it this year, the whole front end needs a refresh.