All of a sudden the OSF suspension has become squeaky when going over bumps. Spring and shock were replaced about 2 years ago and have done about 20,000 miles since.

Drop links and TRE were replaced last year.

Wishbones were replaced with the springs and shocks about 2 years ago.

You can't really hear it with the window up, but with it down it is very noticeable.

Any ideas on where to start?

You could try spraying each joint one at a time with WD40 and see if the noise stops - that may help you identify the source.
Ive never tried it but worth a try maybe. Jules

It is getting noisier, and can now be heard inside. It does make it a little easier to diagnose though as it now does it when pushing down on the bonnet.

I got my wife to see if she could locate the noise whilst I pushed the front of the car up and down.

She reckons it is the bottom of the drop link. That was replaced for the MOT 2 months ago. I'll have to check it out and make sure it hasn't come loose.