How does this look to you?
CASE:
Cooler Master K-350 Black Mid Tower £33.59
PSU:
550W Antec VP550F Black PSU £50.39
MOBO:
MSI Z87-G41 PC Mate, Intel Z87 £68.24
CPU:
Cooler Master Hyper 212 EVO £25.45
Intel Core i5 4670K, S 1150, Haswell, Quad Core, 3.4GHz £167.94
GPU:
2GB XFX Radeon R9 270 Boost (BF4 free) £132.32
RAM:
8GB Corsair DDR3 XMS3 PC3-12800 (1600) £60.96
System SSD:
128GB Corsair Force Series GS 2.5" SSD £57.59
Storage HDD:
1TB Seagate ST1000DM003 Barracuda £41.98
Total = £649.44
Still need an OS and an optical drive (well maybe I've not used my optical drive for 4 years)
You'll see the biggest gains from having a SSD. The CPU will be future proof for a few years at least and the GPU will eat ESO for breakfast. With the MOBO you'll have the flexibility to upgrade the GPU add more RAM and additional HDDs should you require. You may have to consider a different cooler for the CPU should you be interested in overclocking but out of the box it will be fine.