I didn't look at the lowest end one I admit, but I did think the Hot rod was about right and should come pretty close to £750 with the parts re-used from the old computer, and not exact brands and models just general specification and not withstanding my previous advice of reviews, reviews, reviews.
I agree with your points on the power needed for what he's playing right now, but you should really build for what you want to be playing in a few years, I'm aiming for max FPS and longevity for £750+recycled parts. I'm not saying your wrong just that his budget will go further than you think.
Scan went down while I was pricing it up, but off the top of my head;
4670k - £180 (stock cool for now, cheap upgrade to OC later in life)
Z87 Motherboard - £100
760GTX - £200
4GB XMS3 - £25
128GB SSD - £80 (agreed the sandisk ones are great VFM)
XFX 550W - £55
Windows 8 64bit OEM - £80 (might be able to get an upgrade license for win 7 even cheaper)
£720 still got enough left for a new case. It's pushing the budget but it works and nothing will trouble it for a long time. I'd be tempted to swap the SSD for a SATA3 mechanical drive though at that price point. That would ease te budget pressure a lot and cost 0FPS.
EDIT: That reminded me one crucial link for building a PC no-one's put in yet;
http://www.hotukdeals.com/ Always worth checking.