Get an Xbox 360 Arcade for the normal price of £129.99 but with free 2 years warranty from a top UK retailer. Marshall Ward deal is only for new customers and loads of people have had problems with them (see the post).
Also available is the Premium Console with 2 years warranty for £169.
5% Quidco is available which works out at £6.45 cashback
M&S have a good customer service so I think that they will honour their warranty.
I personally think this is a great offer as it also protects against any problems you may get with the system over the next 2 years.