I would also go for a 500w PSU but you wont need much higher.
You havent said what resolution you would be gaming at it which is crucial for reccomending a GPU.
But I will assume its 1080p in which case I reckon a 6gig gtx 1060 or a 8gig rx480 is a good bet, depending if you prefer better DX12 or better DX9/11 performance.
I hope you meant under £300 for the GPU not the PC total
as you wont get a useable GPU for £60.
Edited by Chrysalis (Mon 24-Oct-16 12:57:10)