Also,OP I honestly think some here are just getting bogged down in details WRT to CPUs,as people are just measurebating over things way too much. Lots of people have moved over to laptops for production and image editing stuff due to their portability. Even the best laptop CPUs are beaten by even a £300 desktop CPU in many cases.
Your CPU is ancient,so basically even a £185 Core i5 10600K or Ryzen 5 3600 will destroy it. If anything a bog standard Core i7 10700,with a Hyper 212 plonk on it,with the cheapest not crap Z490 motherboard would be a lightspeed upgrade over what you have. That would be under £300 for the CPU and aftermarket cooler.
The main issue with the Core i9 is the motherboards and cooling you need for it. WRT,to the Ryzen 7 5800X you can get it in bundles withe B550M Mortar for £380~£400 but a CPU cooler needs to be added. The Ryzen 9 3900 non-X bundles comes included with a CPU cooler,and the Ryzen 7 3700X has the Wraith Prism which is just beind a CM Hyper 212 in performance.
Also,one thing is Rocketlake is also due in a month or two. One area which it does improve in a lot is the IGP,so it could be also worth seeing what that brings to the table.
Edit!!
Also if you want to spend less money,but get a decent boost have you tried getting one of those secondhand Xeons for your motherboard? One of them is the Xeon X5670.