If you are stressed about this just take a couple of days to clear your head. There is a massive choice at the moment and in a lot of cases there are only marginal differences between the components, I will take Bragmisters experience into consideration and at times there are large differences as well just like he is showcasing with the X3D chip.
Once you know that a certain component is critical for your usecase you can narrow the components down and focus on that. So for your case it looks like a 5800X3D or wait for the 7800X3D. If you do not want to wait until April then the 5800X3D is a great gaming chip now , will be a great gaming chip next year and the year after and the year after that as well. You can build a AM4 5800x3d build with a 6700/6750xt for under £2000 and will be great for WOW and FM for the foreseeable future.
Add to it that it is a great overall gaming CPU for TODAYS top end GPUs, I am running it with a 7900xTx. At least for two generations (If nothing drastic happens... quantum GPUs?!?) of GPUs he will be fine.
I remember running through a 4690k for like 3 generations of GPUs with no issues.
In other words, If you are trying to future proof yourself... just remember that there will be always something new down the line.
If you are tight on a budget, Take the best bang for buck and return on investment NOW. If you can stretch for a couple of months it is always advisable. Maybe GPU sales crash (which is happening it seems) and you get yourself a sweet deal.
If you can't wait, Put an excel sheet... build everything around the 5800x3D. Anything that can be added later, Add it later.
Main Components are:
1- Cpu (5800x3D)
Order AMD Ryzen 7 5800X3D Cache Eight Core 4.5GHz (Socket AM4) Processor - Retail now online and benefit from fast delivery.
www.overclockers.co.uk
2- Mobo (B550 - X570)
Order Gigabyte B550 AORUS Elite AX V2 (AMD AM4) B550 ATX Motherboard now online and benefit from fast delivery.
www.overclockers.co.uk
Make sure that it comes with latest bios or at least ask them to flash one that can run the 5800x3d and Gigabyte just updated their bios to allow for curve optimizer.
3- Ram
Order Lexar Hades RGB 32GB (2x16GB) DDR4 PC4-28800C16 3600MHz Dual/Quad Channel Kit now online and benefit from fast delivery.
www.overclockers.co.uk
Can't go wrong with CL16 3600mhz and 32GB.
4- Gpu (You have one already)
5- Cpu Cooler (5800x3d Doesn't come with one and highly recommend the AK620 since with a simple voltage offset with the newest bios) but since OCuk doesn't carry it:
Order be quiet! Dark Rock Pro 4 CPU Cooler now online and benefit from fast delivery.
www.overclockers.co.uk
Most decent one avaliable on site. Noctua is good but I see them as overpriced.
Gpu already chosen the rest will cost you 728 pounds. You can find cheaper alternatives elsewhere but these are on this site... now
Case, Fans, Cable mods and everything else can be added later. These are cores of your system.
Minor Edit: Main reasoning I didn't go with AIO as a cooler is well.... I see that big fan coolers are better for Ryzen CPUs, The only real alternative is to go full custom cooling and that blows the budget to the sky.