Right I'm going to keep this nice and simple, I want to buy a gaming PC for 400-500 pounds that can run Minecraft, Garry's mod and DayZ is it possible and if so can you suggest any? Or would you suggest to buy the parts separately?
This build will do you fine. the Graphics card is a bit overkill for what you suggested but it will give you room to grow if you want more intensive games later on. http://uk.pcpartpicker.com/p/BTjTZL
this is a pretty solid build. it comes with everything besides a monitor, keyboard, and mouse. this will provide you with medium/high settings at 1080p.
if you can stretch a little more budget wise, an i5 would be better. you can downgrade the graphics card to get an i5, but would impact your playing settings more