This is the cheapest brand name 240mm liquid cooler by some margin.
Corsair make a particularly fine selection of AiOs, also known as all-in-one liquid coolers. They use off-the-shelf designs for their pumps and radiators, as do many other companies, but distinguish themselves with good-quality fans, optional lighting and low prices for a major brand. That last point is particularly pertinent today, as their H100X 240mm AiO has dropped to nearly £60 on Amazon UK - a significantly lower price than any alternative that I’d rate as highly and some £25 below this AiO’s original launch price.
Altogether, it’s an easy way to give your CPU a big cooling upgrade over a standard box cooler without the clearance issues you may run into with large, high-performance air coolers like the legendary Noctua D15. Most mid-size (and even many Mini ITX) cases will support at least one 240mm radiator, but it’s worth double-checking your own case before hitting ‘buy’.
Reviews of the Corsair H100X are also quite strong. Looking at KitGuru’s writeup at the time, the reviewer noted ‘impressive performance’ from a clean design that was easy to install - not bad! The only minor downside was that the fans ramp up to loud levels at very high loads, but that’s perhaps to be expected from a budget model that doesn’t come with the most premium fans. You could look at swapping these out down the line - potentiallyfor the firm’s magnetic levitation fans- to get a quieter end result.
Either way, you ought to be pretty happy with these fans for the money. You can get cheaper alternatives, just barely, but these tend to be more naive designs - ones from brand names that I haven’t tested and for which I can’t speak of their quality. Still, if you have your own recommendations for budget CPU coolers, don’t be shy - feel free to speak up in the comments!