Been playing this over the past week. It's fun and addictive. I'm getting 90-130 fps average at 1080p with a GTX 970 with most settings on High or Epic. It's assigning slightly over 2GB VRAM so would recommend a 3GB video card model minimum, and can assign slightly over 3GB RAM, so the 8GB is fine. CPU is not all that intensive. No need for many cores, probably benefits from faster cores.
System is Haswell and DDR3 so I'd look for used i5-4670, i5-4690, i7-4770 or i7-4790. £100 for i5 and £145 for i7 were the last second-hand prices I spotted.
For graphics, something like an old R9 380X 3GB or GTX 770 4GB for £50-75 would give 60+ fps on High settings.
So it's doable for £150 if power supply will cope.