Before I go on to fully explain this build I'd like to point out some things in a tl;dr first..
1) The PC will be borrowing my desktops 7850 when being used for gaming, and will only be used for gaming at friends.
2) I understand the PSU will receive some criticism, first its not even that PSU the one I have isn't listed on PCPP, second my very trust worthy PC store convinced me that there's no problems with them (in fact they return more XFX PSUs to the manufacturer than anything else)
3) The gskill RAM you see is from my desktop which is what i originally planned to use, but it wasn't POSTing with it.. not sure why the ram is fine, purchased the Crucial and now works fine
4) Total spend £310
5) OS will be dualboot windows for gaming and there will be linux for when used as a media PC - linux would allow for much easier network access to the files
Something fast and cheap, I didn't feel the use of the PC warranted an i5, and if it did it would have been a K series.
With the i3 any board would have been fine, so I went for B75, they are the cheapest boards available that natively support IB (without a BIOS upgrade on arrival). The B75M-ITX from ASRock seemed a perfect match, cheap, has everything needed +more. Nice too see the USB 3 header. Some of the IO headers are in non default places due to the form factor of ITX though it wasn't harsh.
The CM Elite 120 is an amazing case for the price, its very easy to work in (though my small hands probably helped). The layout is very good, and I found it very easy to cable manage inside. The Full size PSU option is great with the right PSU. The USB3 port on the front does use the internal header not a pass-through too. For a cheap ITX build I highly recommend the case!
So initially my intentions were to get an XFX 450W core edition, but my local PC store had ran out of held stock. They unfortunately happened to have very poor stock of low wattage PSUs in so I ended up with the OCZ CoreXstream edition 500W (not the similar one I have listed) . Now I know this isn't a great PSU and there are some issues, 1)The sata lines on it are not long enough for 1 line to stretch to the HDD from the ODD so i've had to use both. 2)Not all braided cables.. Though I must say that there isnt excessive cables on it.
The rest of the parts are fine, HDD is great, have one in my desktop too, RAM was nice and cheap for what it is, crucial is a very good brand and I have no quarrels.
Overall I am really happy with the outcome of this build.