mmartin1995 :
£450 and below. Really want something that will be able to game in 4k too
for 4k, you need at least twin GTX 780s or r9 290s.
But if you want to just get one gtx 780 or r9 290 then get another later then that will work.
also, get a 6GB gtx 780 or 4GB r9 290, don't get a 3GB model or lower