Well... how much does the 750W cost? I know a really good, silver rated one called PC power and cooling silencer mk ii 750W silver rated... it's $110 in the US, so I don't know how much it would cost where you're buying it. Also, I'd get DDR3-1600 RAM. Please check that the RAM is 1.5v. Other than that, everything looks great!
The site is actually quite annoying in that regard, only giving relative prices. The 650 watt version is £8 less, so not a big deal.
The 1600 RAM is £68 more for the same 16gb, which isn't bad, but I'll shop around and see what prices are at places like Crucial. It doesn't give the voltage but I'll check that out too, thanks!
Overall I need to find another component site, this is the only UK based one I could find a recommendation for, but not having the prices up there is a pain in the neck.
The Antec Eartwatts 650w is $50 on Amazon.
Get the i5 2500K and do a VERY easy overclock to surpass the i5 2550K.
They are running a 'spring special' which involves a free upgrade from the 2500k to the 2550k, so effectively the same price. The 2550k should be overclockable too right?