First of all:
PSU model?
Ram specs?
Mothetboard specs?
At the moment I would completely change platform to amd as it is quite future proof, cheaper and better in price per performence compared to intel:
Ryzen 5 2600 (100-120£, there might be even a sale under 100£)
For RAM higher speeds are really usefull when using AMD. Atleast ~3000mhz is recommended (it will also work with lower speeds, but the slower the more fps loss you will get)
So if you have atleast 2933mhz ram, I would look for the exact same stick. If not, the 2x8gb g.skill aegis kit is the way to go. (50-70£)
And a b450 motherboard. There are plenty for under 70£. I have an AsRock B450M Pro 4 and I'm very pleased with it. It has all headers you'll need, even some rgb headers for some fancy upgrading. I'm really enjoing it.
Hope I helped you