A friend of mine just got himself a second hand 4970k, 16Gb DDR3 1666, GTX980, SSD 512 Gb, 3Tb HDD, Gigabyte mATX mobo, Noctua cooler, BeQuiet PSU and 27" screen for just 1200 Euros (around £900?). So I think a decent machine is quite afordable nowadays in the second hand market, no need to get such an old platform. I would try to get the best CPU and GPU available withing your budget, that is what you need for sim racing. The rest is not that important, you can invest in a proper wheel.