Rough guesstimate:
RAM £56 SSD Samsung M2 NVMe 256GB £53 AMD Ryzen 5 5600G CPU £230
So about £509 inc VAT
(The m.2 posh wifi and BT card with external aerials is about £20, but a bog standard USB wifi for £5 - £10 would do the trick)
If you don't mind a more cuboid form then:
Not unreasonable prices for that spec in the current climate... you can trim a bit going up to larger small form factors boxes - but not huge amounts. Eg, a ready built HP 290 G3 SFF PC, i5-10500, 8GB, 256GB SSD, WiFi, Bluetooth, No Optical, Windows 10 Home, 1 Year on-site is currently about £475, and then you would need to add another £20 of RAM to get to spec. (but you do get a copy of Win 10 home you probably don't want!)