Hi Blondi,
I’m in the UK too, and have found CCL to be competitively priced and have good customer service. Generally very quick deliveries too, although if you’re in the highlands or islands it may not be so good.
Obviously and as noted above, try the other big shops like Scan and OC too. With a few calls and a bit of online research you’ll be able to work out a good spec.
With the resolution you want to use (plus for VR) you’re going to need a high end graphics card like a 3080ti, and a similarly high end cpu & motherboard and a decent power supply to tie it all together. If you can it’s a good idea to wait until later this year, either for the newest generations of CPU and GPU, or to take advantage of a bit of a discount on the current high end stuff.
32 GB of fast RAM and the quickest M2 NVmE drive you can find for the sim should complete the tower, then you just need to think about the VR headset and your yoke & pedals or joystick, have fun!