Lol np, I'm just a random guy who likes this stuff and recently got laid off due to COVID so I have too much spare time. I've got savings so I'm good financially until I find a new job. The build I gave you previously is already pretty much top notch (also has one of the best CPU coolers included, the Noctua NH-D15S) when it comes to gaming and most other things. The only thing left to upgrade that would impact gaming in a meaningful way is the graphics card to an RTX 3090 but you would be paying +1000£ more for a pretty insignificant upgrade that would only really matter if you had a 4K display. You're better off saving your money and using it to upgrade in a year or two to the RTX 4000 series or AMD equivalent which are rumoured to have a massive performance increase.

There exist a open source activator on github that will generate a real digital license for you right on github. It works by essentially abusing a loophole left by the free Windows 7/8 to 10 upgrade offer and Microsoft doesn't care since they make the vast majority of their Windows 10 profits through OEM and busienss deals along with other means. Github is owned by Microsoft so funnily enough they kind of self-host this tool. I've also coded my own activator using the same principles that lots of people I know both offline and online use and have been using for years with no issues. After the activation is finished you can even reinstall Windows and your activation status will stay since it's a digital license tied to a hardware ID stored on Microsofts cloud just like what you get by using a store bought key or by buying a license from Microsofts own store.

Oh and as far as Windows goes you can still activate Windows 10 with an old Windows 7 or 8 key, or transfer an old Windows 10 license to your new build. I don't recommend buying any of those cheap gray market keys since from a legal standpoint they're no different than using an activator and infact they're less reliable long term since they're often sourced through questionable means and get blacklisted later down the road. If you don't have any old licenses and don't feel like paying the frankly absurd full retail price for a Windows 10 Home or Pro license then HWID activators are also a good, albeit less than legal option (though not any less illegal than running unactivated or with a gray market key neither which give you the legal immaterial licensed right to use Windows).

If you have a high refresh rate monitor, don't care much about ray tracing and prefer high FPS titles go with AMD. Whichever you choose though the differences aren't really that massive. The AMD GPUs seem to be easier to find at somewhat reasonable prices and personally since I'm mostly interested in high FPS and have a 1080p 390hz monitor I'd get a 6800 XT.

Hopefully I didn't forget anything but that should be the gist of it.

The AMD Radeon 6800 XT is about equal in performance to Nvidia RTX 3080 with the 6800 XT being on average slightly better running at resolutions below 4K while the 3080 is slightly better at 4K. The 6800 XT is also better in high FPS titles such as CS GO due to it having a hardware scheduler while Nvidia GPUs do scheduling in software. Nvidia GPUs on the other hand while worse at titles like CS GO have better ray tracing capabilities. In the end it boils down to what you're mostly looking to do. If you want to play the latest ray tracing enabled titles on a 4K monitor then go Nvidia.

(continuing still)

Just as I was finishing a pretty long reply my phone ran out of battery.. anyway here it goes again.

As far as prices are concerned they're more likely to further increase rather than go down as the chip shortages are predicted to worsen, sadly.

To my knowledge, however valid that may be seeing how I'm not from the UK myself , Overclocker.co.uk should be one of the best PC hardware retailers in the UK. Their prices and stock seem good and they're the ones I see mentioned most often when people discuss UK retailers.

(continuing in other comment since I ran into the 1000 character limit)