Firstly, in addition to having a terribly structured website, I find that OCUK is regularly overpriced in comparison to scan, dabs and ebuyer for UK components. I guess it's because of their forums following and the references and recommendations they get from their members they can afford to, but I digress.
http://www.scan.co.uk/Products/ProductInfo.asp?WebProductID=397203
Same product, £8 cheaper.
How to install a hard drive:
http://www.mechbgon.com/build/harddrive.html
When you've got it hooked up, boot your PC, go to your My Computer, find the drive and right-click and select format. Format it for NTFS.