What is the best CPUs and GPU I can get for £250/$400?
This is disregarding the motherboard, PSU and anything else, just focusing on the CPU and GPU.
This build will be for gaming, not anything major though.
DON'T go for AMD APU, your best choice for that budget is an AMD R9 270X (£150) and an FX 8320 (£110)
If you don't want to spend the extra £10 for 8 cores go for the FX6350