Just found this. The hole in heat shield is bigger. Like the heat shield has been pulled out over the remaining clip. https://www.google.com/url?sa=t&source=web&rct=j&url=%23&ved=2ahUKEwjwvra2m7DkAhXIQUEAHdtmDGEQxa8BMAJ6BAgAEAY&usg=AOvVaw0VTJzWxrN8ZFOD4xbU2nov They are a different type of part than the one used on the under bonnet sound proofing, so just buy some, but, be aware that in most cases, the original retainers will still be on the car but rusted up, and the reason that you are finding that the heat shield has fallen down is because it is made of some aluminium alloy kind of material, and these retainers are zinc'd steel - so that has started a reaction that has locally trashed the aluminium alloy material - and it has "gone" and the heat shield now has a big hole in it where originally it had a small hole for the retainer's stud to pass through. So that means that you will need to make up some thin metal disc patches/repair washers to cover these holes when you go to fit new retainers. I scraped out all the iron oxide rust and the hole in the heat shield is a circle, like it has always been that size. The heat shield looks in good condition. I've got some washers that will cover it though.

As for fitment, I guess they just push over the screw stud that is peeping out the heat shield, and has lots of rust on its surface?the heat shield now has a big hole in it where originally it had a small hole for the retainer's stud to pass through

The heat shield has two little tabs that retain the washer/clip. Bend them down slightly to remove old and fit new. The stud has a screw thread. So after initially pushing the washers on, can rotate them through one of the slots to tighten slightly. Car exhausts work hard to protect the air and the environment from dangerous emissions. At Halfords, we have exhaust essentials, including premium parts, clamps and gaskets, and other accessories. We also supply OEM parts, including DPF sensors, diesel particulate filters, catalytic converters and Lambda sensors.