How about this one:
http://configure.euro.dell.com/dells...1911&x=12&y=11
3.0 P4, X600 graphics etc,
I get that to £657 with 1024mb memory, taking off the onsite warranty ( you dont need to pay for on site warranty if you have a friend who can repair PC's

)
you could add the built in card reader for £23.50.
Almost the same spec as Medion, but with faster CPU, but it is a Dell for less money than Medion
Cheaper to add more hard drives yourself (or your friend) later !
for example a maxtor SATA 160gb is only £45 + VAT at ebuyer,
Another big advantage of Dell machines is that they are almost silent.
when a shop builds a cheap PC they usually use a cheap CPU fan and cheap PSU, both are noisy, Dells are almost silent
Hardly worth building your own PC when you can buy them pre-built that cheap !
Mark.