Thanks for the webnote,
The most popular size of tubing seems to be 7/16, it is in a lot of the kits that we do and is the one that i sell the most of.
http://www.overclockers.co.uk/showproduct.php?prodid=WC-107-PM&groupid=962&catid=1530&subcat=1775
Then i would recommend some compression fittings to keep your loop tight...
http://www.overclockers.co.uk/showproduct.php?prodid=WC-103-XS&groupid=962&catid=1529&subcat=2584
If you are only cooling your processor then you should only need a dual radiator and a good but not overly expensive pump.
If you have enough bays in the front of your case then i would recommend a pump/res combo...
http://www.overclockers.co.uk/productlist.php?catid=2133&groupid=962&sortby=priceAsc&subid=2134
If you are planning on cooling your graphics later as well thent he d5 pump is one of the best..
http://www.overclockers.co.uk/showproduct.php?prodid=WC-140-XS&groupid=962&catid=2133&subcat=2134
You wont need anything that powerful just for the processor though.
The coolant would be up to you depending gon what colour you would want.
Mayhems are very popular.