Nvidia gtx 650 1gb direct cu - £110
I'd expect to have paid a bit over £80
The mobo, cpu, and ram was a bundle, that was £330 for an i5 hasswel quadcore 4430 3.0ghz, 8gb of ram, and the H81M.
That's £270
on amazon
The case was around £55, and the PSU was £70, windows 8 was 80, and the networking card was £30
Depends what case, what PSU, etc, but based on other items, looks like you could have saved at least £100, possibly more.
Ultimately, you could have bought a similar system off the shelf for less: For example,
here at £700. And that comes with a 3 year warranty.
But don't beat yourself up! In a year the system will be massively out of date and overpriced anyway, that's the way of these things. I write this on my Q9550 with 6Gb of RAM, built just when the i3,i5,i7 ranges launched. I spent less, and saved a bit in the process, but I've probably spent more just in electricity as a result lol!