Here’s the before photo. I just used peroxide based hair lighter from boots. The solution when all mixed up to do the hair is actually a paste. I just brushed it on the plastic bits I wanted lightning and placed it right in front of an ultra violet light (black light) I have in the games room and just left it there for 24 hours. You can also leave it on the window sill for a few days in the sun. The decals weren’t affected, just the plastic. A few weeks previous I also used really smooth sandpaper to take a layer off the top surface and that also lightened it. There is loads of info on the internet about de-yellowing plastic - sorry I thought this was common knowledge.