If you need WiFi then I'd go with the mATX build I suggested in my first post above then
If you got the budget for another £30, I'd use the
Arctic Freezer 34 Esports cooler for the CPU, instead of the stock one.
Obviously if you want a different case then go for whatever you fancy, just make sure it's got good airflow and at least micro-ATX size. I would've originally suggest a standard ATX build, but those motherboards are more expensive, the B550 boards with integrated WiFi start at £195. So I'd go mATX to include WiFi at a decent price, unless you really want an ATX case/board
Mouse/keyboard wise, there's lots of options - depends on your personal taste really. Mouses like the
GPG Model O,
Razer DeathAdder v2, Logitech G402, SteelSeries Rival series mouses, Corsair M55 / M65 / Harpoon / Scimitar and the Logitech G402 are all decent for the money. Then keyboards you have Razer Cynosa, Corsair K55, SteelSeries Apex 5, or if you wanna go mechanical there are hundreds lol.