Looks like a 120 mm AIO in there... is the case too small to fit a 120 mm air cooling option? Only then is it worth it at all... remember, the entire point of watercooling is being able to use a nice big radiator without having to fit it right onto the CPU.
Yes, it would have been a little cheaper (maybe £20) to buy a well performing air cooler for the CPU. However, i've been water cooling PCs since the early 00's - custom water blocks for CPU, Northbridge and GPU, Ehiem pumps, water wetter, all that stuff! - I would find it strange to go back to air.
I also don't like the thought of hanging a heavy air cooler off the motherboard - I prefer the weight attached directly to the case (yes I realise that the water block with integrated pump also weighs something ) and I don't have to worry about clearance for RAM or other motherboard components.
The case is a CoolerMaster Silencio 352 and it will happily accept a 240mm radiator in the front. But as i'm not OCing anymore, I didn't feel the need to spend any of my budget on a large radiator.
I don't recognize the board, what model is it?
Nothing too fancy: https://www.gigabyte.com/Motherboard/GA-AB350M-Gaming-3-rev-1x#kf
It has fairly decent fan control, but I have more fans than headers and the Noctua controller gives me a bit of additional control.