I bought many components from Amazon for my last build which was only couple of months back. Overclockers for the others.
Currently the absolute best ganing processors are the Ryzen X3D processors, 7800x3d last gen, 9800x3d is the current gen (both use AM5 platform). They're out of budget now, but its good to consider the upgrade path as these really are amazing CPU's
Motherboard - I'd suggest a b650 (AM5 platform) motherboard, my pick was the tomahawk b650 wifi, a great board at a fair price when i purchased it, but there are a ton of options so it all depends on the current offers as to which would be the best value. Definitely avoid
CPU - Ryzen 7600 circa £190, or if you're inclined to save a few £££, ali express sell the 7500f for around £110 delivered. Its basically as quick but for a lot less money.
RAM- a pair of 16gb (total 32gb) of 6000mhz with CAS 30.
PSU - depending on what the future plans are, you can use a reputable 600watt with a moderate GPU. If you're looking tp upgrade to a top of the line graphics card in future, you'd want to consider 850 watts or more. Go for a gold rated, preferably modular.
GPU - the intel Arc B580 are a probably the best price to performance pick right now. However, next gen graphics cards are just coming out so advice would be to wait at least another month before committing.
Case - there are so many options here, you can go full flashy lights for very little money if that's your sons thing (most people seem to favour it). Just check compatibility for motherboard size (ATX, micro atx, mini itx, or the even more rare E-ATX). I always opt for standard atx, it gives the most options. But you still have quite a few for the micro atx standard if wanting a smaller form factor.
Never buy windows from one of the system builders, they usually charge £100+, but you can buy the same thing from SDC keys for approx just over 11 euros as of now.
Any pre built machine will add circa £200 to the cost so I would try the self build route. They also often cheap out on inferior power supply or slower RAM, so you can get a better PC for your money if you can do it yourself.
There are a lot of videos on YouTube to guide you here. It really isn't as scary as it might seem.
PC gaming has so many advantages over PlayStation and Xbox. The modding scene for example, you find way more mods. Old games become almost unrecognisable and appear like an entirely new game for free (fallout 4's "Fallout London" for example)
The textures are also far superior with better refresh rates (obviously you have to get the right components which is costly)
If you want updated advice, the youtube channel geekawhat is very good and has many videos on the subject. He often shows different price point PC builds with the recommended components.
If your son is serious, and it sounds like he is, learning how to build would benefit him longer term as he can get a lot more for his money. Plus it's quite exciting putting it all together. Maybe it could be a nice son and dad task?
A decent monitor is also needed and can be very costly.
1k is a good starting budget for the PC build. You're 100% right on doing your research, curry's are OK, but they're selling older spec models which don't stack up well on a cost to performance ratio in my opinion.
I wonder, will your son be looking on the Bank of Dad to support him.........