I heard that toshiba laptops are good for multimedia editing
and i heard also that the red sub laptops are very very good for video editing... and the sony "VAIO" laptops.. but they all come up to well over £1000
but to be completely honest i would not recommend a laptop at all for the price of £900 for video editing - too many limitations - especially the screen limitations. i know that laptop technology has REALLY advanced but still, i recommend desktop computers for this type of thing. it is too common that many laptops have very good fire-wire ports but extremaly poor video display technology and vice versa. i'm assuming it would be cheaper to go with a desktop pc... laptops are usually more expensive when it comes to video editing and upgrading... and it is very hard to upgrade them
i'm not a laptop expert though just my opinion