CPU: Motherboard: Memory: Storage: Video Card: Case: Power Supply: Monitor: Total: £705.53

Grab any cheapo keyboard for now.

I'd ideally be looking at a decent ultrawide monitor or 1440p mo ...

What is your budget and currency? I'd like to try spend around £700 max.
What will you use the PC for? It will be used for gaming. Mostly just Old School Runescape.
Do you need a monitor? If no ...