List everything you have.
Thanks for the advice so far guys, really helping a lot.
Here is what I've got:
i5 2500k clocked at 4.1ghz, under an antec cooler (pretty good system, happy with it).
Board is a gigabyte p67a-ud3p-b3 with 12gb of 1600 ddr3.
SSD and storage HDD, with Win 10 preview.
Can't remember the model of PSU, it is an antec and had reviewed really well in Custom PC magazine (added this about eighteen months ago, so would imagine it'll still be fit for purpose - will obvs check before purchase).
All in my CM 690 model 2 case. Looks a bit tatty but nice and big.
Really coming round to the shiny new high res monitor and graphics card option. Would be good to buy the monitor this month and maybe wait to see how the new cards come out next month.
Thanks again troops!