Hi there
Just would like some help on a computer build I've been considering. I want to take a cheap PC and add a CPU, GPU and some extra Ram to it and then play CS:GO. I would like to play it at a quality similar (or above!) console standard!

Here are the links to the parts I have looked at
MAIN Computer
http://www.ebay.co.uk/itm/Dell-OptiPlex-380-Desktop-PC-Intel-Core-2-Duo-E7500-2-93GHz-2-0GB-DDR3-FREE-P-P-/291723934212?hash=item43ec19fa04:g:-EcAAOSwzvlW9B1E

Intel Xeon
http://www.ebay.co.uk/itm/INTEL-XEON-X5460-QUAD-CORE-PROCESSOR-3-16GHZ-12M-1333-SLANP-SOCKET-LGA771-/172134260926?hash=item28140060be:g:icYAAOSwYIhWlBPY

GPU
http://www.ebay.co.uk/itm/ASUS-Nvidia-GeForce-GT-630-2GB-Graphics-Card-GPU-/322041220944?hash=item4afb270f50:g:qEYAAOSwoudW6DRq

Ram (could I buy multiple to enhance gaming?)
http://www.ebay.co.uk/itm/1GB-1x1GB-DDR2-533-PC2-4200-Memory-RAM-Upgrade-HP-Compaq-Gaming-Series-Desktop-/231509615260?hash=item35e70c629c:m:mZLZZptSRUzxGhEpm_OiXuwI would advise against those parts.  The machine is a small form factor desktop design which isn't big ENOUGH to fit any REASONABLE video card (including the one you linked).  The CPU is ALSO not compatible with the motherboard without using some sort of dodgy 775 to 771 socket adapter and even then it's down to luck if the BIOS will support it.  The machine you linked uses DDR3 memory so the DDR2 memory you linked also won't work.

At the very least you'd be best looking at regular desktop tower systems with something like a Core 2 Quad included then upgrade the graphics card accordingly.  I would however STRONGLY recommend saving for something better rather than pumping money into an already old computer.  CS:GO is already pretty old so you won't need much, even modern integrated graphics would be enough.  You could buy/build something using integrated graphics for now and then upgrade it with a decent video card later on.