Average gaming computer doesn't really need any super high airflow.
Though if you overvolt everything and crank up clocks, that can fast cause major increase in heat output.
There's simply huge possible variation in cooling needs, depending on parts you have and how they're used.
Nicely versatile Define R5 would be that £100
https://www.overclockers.co.uk/fractal-design-define-r5-midi-tower-case-titanium-ca-034-fd.html
Less fashion crud than in R6 actually makes some of PC's assembly work lot easier.
While not in OcUK's stock R5 is definitely available.
Define C would be no external bays-fashion design with less versatility and more fashion crud to obstruct ease of PC assembly.
("PSU shroud" has zero technical justification in modern PC)
Also for £100+ BeQuiet has some quite nice designs with less "cubic" outlook. (Silent Base 600/800)
Such shame that instead of proper mass damping of side panels, those use light thin cosmetic fraud foams...
BeQuiet even makes excellent combination (2mm bitumen+8mm foam) damping mat.
So there would be some work for realizing silencing potential of case, by first removing those fraud foams and installing for example some bitumen car acoustic mat in place of them.
(and unlike in Define R5 and R6 you can't access their bottom dust filter from front and you need to turn case around)