Thanks everyone for the inputs!

I managed to take out the airbox, and undo the belt.

After playing around with the separate components, I realise that the steering pump is main source of rattling noise.

Pushing the steering pump pulley back and forth, there is a bit of play. I suspect the bearings are shot. Other pulleys are quite solid.

A couple of questions:

1. Would it be best to change the ENTIRE steering pump? Or is there a way to just change the bearing / pulley portion?

2. Is removal / reinstallation of the steering pump a big job? Or a simple plug / play thingy?

This is my first time working on my car and thanks to help from this forum, I actually think I might be able to DIY my problem!

Thanks again!