UK - Moving from Gaming Laptop to a PC after 5+ years. £1500 Budget.

For reference I've been using this for the previous 5+ years but its starting to struggle a bit and some newer games I have to turn down to lowest settings or not even be able to run them at all (POE2 I had to just give up on for example) - ASUS ROG Zephyrus

• New build or upgrade?
  • New Build
• Existing parts/monitors to reuse? (List with models/links)
  • Reuse Monitor - Dell S2721HGF
• PC purpose? (Gaming, editing, etc. List apps/games)
  • Gaming - mostly older less intensive titles like WoW Classic, Civ, ONI, Factorio but I also want to be able to play newer titles without having to turn them down to the absolute worst laggy settings
• Purchase country? Near Micro Center?
  • UK based. Would prefer to purchase online. Happy to spread the purchases out over next 2-3 months.
• Monitors needed? (Number, size, resolution, refresh rate)
  • No
• Budget range? (Include tax considerations)
  • £1000 - £1500
• WiFi or wired connection?
  • WiFi now, wired later probably (renovating house currently)
• Size/noise constraints?
  • Ideally on the quieter side
• Color/lighting preferences?
  • None
• Any other specific needs?
  • Want to build it myself, would be first time building a PC, I can follow guides but ideally idiot proof!