Just over £2100.
On top of the base cost, I uprated the stock RAM to 2666Mhz DDR4, added a soundcard, specced the use of Arctic Silver thermal paste and paid a few quid extra for their 'elite cable management'.
After one night I have to say I am absolutely delighted, it looks fantastic (to my eyes, my wife was less impressed that my base unit has grown again - "I thought technology was meant to get smaller as time passes?") and runs like a dream.
I was a little worried about speccing a Windows 8 build, but did not want the 7 Home Premium option as it would limit the usable RAM to 16Gb (and the machine has 16Gb plus 4Gb on the graphics card), but they installed and configured 'classic shell' free of charge, which effectively gives me a Windows 7 desktop.
So far I have tried AssCreed Unity, Crysis 2, ARMA3, Dying Light and Elite Dangerous (ofc). Suffice to say, performance is off the scale. I don't have any benchmarking software (which Lee moaned at me for) but on all the titles, with everything maxed it is silky smooth, nary a judder or flicker in sight. The only sign it gives is a slight whoosh as the fan speeds ramp up.
I have not got everything arranged to my satisfaction yet, but once I do will give you a 'cockpit view'