Grey/silver

Adore Platinum is very blue/green, it looks a lot like diluted Blue Black. You can make it a truer silver by adding some pink or violet.
Silver dyes are really just blue or purple, I haven't found one that is genuinely grey. So they are very dependant on your base. In my Avatar pic (which was more silver and less white IRL, although it was faded and ready to be touched up in that pic) I had Pravana silver on the freshly bleached roots, but the rest of it was various homemade toners over the green, yellow, pink and lilac my base had faded to.
So if you can fade your purple you will either get lilac then white if you have a perfect base, or a silvery grey as the faded purple tones any yellow in your base. At this point you can go in with a custom mix of toners to even things out.
If it fades pinky, the Adore Platinum will be ideal. However it fades you should be able to incorporate the fade into the grey
So sorry for the long waffly answer, TLDR version, fade it and then decide what colour/s you will need to tone to create silver/grey from your fade.

Thank you for the long waffley answer  😉 I'm glad it should be pretty easy to get from my current colour, I've used a mix of colours for the purple I have now but it's mainly Adores Purple Rage so hopefully it'll fade pink then I can use the Platinum  🙂