I selected the Aero G motherboard for you. It's a no-brainer really. Similar price, better VRM, better M.2 slots, better memory speed compatibility (though you should be aware that fast DDR5 is very expensive and probably overkill today).
These are three M.2 slots:
no.1 is 5.0, connected to the CPU and causes PCIe to drop from x16 to x8
no.2 is 4.0, connected to the CPU as well, and doesn't block the PCIe slot
no.3 is 4.0, connected to the chipset. Doesn't interfere with PCIe
I swapped out your Pop XL case for a Define 7 Compact. The reason is the Pop does not come with a USB-C port, just the placeholder. But you can buy it from Fractal if you really want that Pop case.
I upgraded the power supply. At your budget you really should not be wasting time with less than platinum efficient units. Your 4090 needs power but when it's idling, you want an efficient PSU at lower power usage.
I couldn't find the Super Flower Leadex Platinum SE 1200 W 80+ Platinum for sale. That would have been my no.1 pick. See if you can find it. The Dark Power 13 Pro is the best, but it's over £300. Maybe you don't want to pay that much
Your cooler choice is ok. Might get buzzy at high temps. The Phantom Spirit EVO is one of the best air coolers so i selected that one. Alternatively you can try the Japanese Scythe Mugen 6 which should be quieter and possibly more durable. Costs more.
The Noctua NH-D15 is a great and quiet cooler. Costs much more, but there you go. None of the three will let you down.
For RAM i had to change your original pick because the Aero G doesn't have it listed as compatible.
The G.Skill Trident Z5 RGB 32 GB (2 x 16 GB) DDR5-6600 CL34 Memory is fast, compatible and white, if that matters. Costs a bit more than the
G.Skill Trident Z5 Neo RGB 32 GB (2 x 16 GB) DDR5-6000 CL30 Memory.
Take your pick. Both are good choices.
PCPartPicker Part List
CPU: AMD Ryzen 7 7800X3D 4.2 GHz 8-Core Processor (£348.15 @ Amazon UK)
CPU Cooler: Thermalright Phantom Spirit EVO 69 CFM CPU Cooler (£46.90 @ Amazon UK)
Alt. CPU Cooler: Scythe Mugen 6 Dual Fan 60.29 CFM CPU Cooler (£66.40 @ Amazon UK)
Alt. Alt. CPU Cooler: Noctua NH-D15 chromax.black 82.52 CFM CPU Cooler (£109.95@ Amazon UK)
Motherboard: Gigabyte B650 AERO G ATX AM5 Motherboard (£251.77 @ Amazon UK)
Memory: G.Skill Trident Z5 RGB 32 GB (2 x 16 GB) DDR5-6600 CL34 Memory (£154.92 @ Newegg UK)
Alt. Memory: G.Skill Trident Z5 Neo RGB 32 GB (2 x 16 GB) DDR5-6000 CL30 Memory (£129.99 @ ebuyer)
Storage: Crucial P5 Plus 2 TB M.2-2280 PCIe 4.0 X4 NVME Solid State Drive (£205.00 @ MoreCoCo)
Storage: Seagate Barracuda Compute 8 TB 3.5" 5400 RPM Internal Hard Drive (£146.99 @ Amazon UK)
Video Card: MSI SUPRIM X GeForce RTX 4090 24 GB Video Card (£1955.98 @ Novatech)
Case: Fractal Design Define 7 Compact ATX Mid Tower Case (£88.99 @ CCL Computers)
Power Supply: be quiet! Straight Power 12 1200 W 80+ Platinum Certified Fully Modular ATX Power Supply (£202.26 @ NeoComputers)
Alt. Power Supply: Super Flower Leadex Platinum SE 1200 W 80+ Platinum (£ n/a )
Alt. Alt. Power Supply: be quiet! Dark Power Pro 13 1300 W 80+ Titanium (£334.27 @ NeoComputers)
Total: £3400.96
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2024-04-07 20:08 BST+0100
Balls. Your GPU is quite long. You will have to move the included 140mm fan on the front of the case to the top position, and you will not be able to use the lower fan pos.
Sorry.
The Define 7 doesn't have this limitation in it's open layout:
Fractal Design Define 7 ATX Mid Tower Case - costs more though:
https://uk.pcpartpicker.com/product/C76qqs/fractal-design-define-7-atx-mid-tower-case-fd-c-def7a-06