Best Upgrade Suggestions for Ryzen 5 3600 and GTX 1080

Hey everyone! I'm in the UK and I'm looking to upgrade my gaming setup. Right now, I'm using a Ryzen 5 3600 CPU and an 8GB GTX 1080 graphics card, and I feel like my gear is a bit outdated since I've just gotten back into gaming. I want to upgrade without changing my motherboard, which is an MSI X570-A AM4. A friend mentioned that I might be able to use some newer CPUs if I perform a BIOS update. I'm hoping to get the best value for money with my upgrades. I found a Ryzen 7 5700X3D for £210, which seems like a good pick. However, I'm struggling with graphics cards as I want to keep my budget around £450 for both upgrades combined, so I may have to buy a used GPU. Any suggestions on what I should look for? Thanks in advance!