I recently had some rattle from one of the Supercharger belt pulleys or maybe tensioner so contacted British Parts for replacements. However they told me that for this particular engine year there was no like for like replacements as the whole assembly had been superseded. The single new part arrived looking completely unlike what I was expecting but did indeed turn out to be correct. A point to note is that it also includes an attached idler pulley for the accessory belt so you need to release that belt too. Here’s a pic of the new part. You also need a different length SC belt and the separate upper idler pulley.