No-one?
$630 US for a 3-year-old gt 540m and an old generation i5 is too much for most people on bitcointalk. Plus, your UK location puts off most US based customers--who don't want to pay shipping from UK.
Finally, Alienware computers tend to depreciate in value much quicker than other devices, because of their inflated retail price.
Ebay might actually be a much better choice for you, people are usually willing to pay a lot more there.