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You're a student so you're eligible for the student discounts. With the Higher Education discount (just call them up when you order), you can get the base spec Mac Mini for £449.65 and you also get three years of warranty instead of the standard one year.
 
For basic tasks like you mentioned you'll even be fine with a Mini G4. And all this talk with Snow Leopard, like you'll even be using any software that will take advantage of OpenCL. SL will only enhance the apps that is coded for it.

Have you ever considered signing up for a ebay credit card and purchase a Mini through there? Are you dead set on a Mini or would a Macbook be better for you since you won't have to worry about purchasing a PS/2 adapter and if it'll even work for your kb/m. At least with a MB, you won't have to worry about purchasing any additional components.

You can find earlier MBs with C2D for the same price as a Mini. Since you are a student, portablity would probably be a better option.
 
I'd highly suggest a refub 2009 Mac Mini over the 2007 model, the cost between the two is minor if you're going to be using this machine for an extended period of time
Thing is, he's in the UK and and Mac Mini refurbs seem to be VERY rare. Haven't seen a 2009 on there at all and I do check fairly often
 
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