I've got a decent laptop, but with it being small, n a load of other stuff, i dont like it for everyday, at home use, so I want a Desktop. I was looking on Aria, and found that getting one of their packages, is cheaper than buying all the parts for it. So now im stuck at which one to get. I'd say my budget is about £300-£400. I wouldnt mind having to build it myself, but if its cheaper, then a package will do. Oh 1 small thing, is buying a Mac a good idea?

Mac, not on your budget. Other then that look around and, check out newegg, to try and price building your own.