The Core i5 12400F is a surprisingly excellent gaming CPU, offering the power of Intel's new Alder Lake architecture in a simple six-core twelve-thread configuration. The CPU supports PCIe 5.0 and DDR5, but it also works with cheaper DDR4- and PCIe 4.0-based hardware.
It's normally £200, but it's down to £167 on AWD-IT which is a pretty decent deal if you want to build a powerful gaming PC on a budget.
The 12400F is an RPS favourite, with James' 12400F review stating that "even without E-cores, the Core i5 12400F is a gaming CPU bargain". It outperforms the AMD Ryzen 5 5600X in games like Shadow of the Tomb Raider, Total Warhammer 2 (yes that's the real name of that game), Total Warthreekingdoms (also correct), Forza Horizon 4, Metro Exodus, AC Odyssey, AC Valhalla and Watch Dogs Legion. Normally it's a fairly close contest, but in AC Valhalla the differential is a solid 19fps - 98fps average for the 12400F and 79fps for the 5600X.
If you'd like to see how the 12400F compares to your existing CPU, you can run the Cinebench R20 benchmark to get a rough sense of things. The 12400F got a score of 4764 in multi-core and 643 in single-core results, with the former being the limiting factor in many games while the multi-core results are a decent indicator of content creation performance for tasks like 3D rendering or video transcoding.
Overall, the 12400F is a strong option at £167, with the 5600X normally more expensive at £170. If you're interested, check out the link above, and if you have any more questions get in touch via the comments below!