Eh, £450 is a bit overpriced. For £450 you could get something with an i7. The 280M in SLI isn't bad, but the 280M is an old architecture and not all games support SLI. Although it's showing its age, it will still be able to play a lot of games on high settings at least.
If you want to go for it, I think closer to £400 would be better. The hardware is good, but depreciation really hurts the value. That and the fact that it has Vista, only 4 GB of RAM, and a small hard drive make for a cheaper system.
to it's credit - the specs hold up to a gt 750M - can play 1080 at medium settings. and retail laptops with those start at around £600 depends if you've got the budget for a better one and do you really want to lug a huge brick laptop around