Doubt the dv2 will be near £500 quid tbh, not if the US price is anything to go buy.
Considering the poor build quality, lack of run time and poor multitasking the dv2 isn't worth the premium over NC20, especially when you not going to be using the better gfx which is one of the few clear advantages it has.
If 2kg is your only hard limit have you considered a dell e6400? Thier 1.95kg with a 14.1" screen, work just gave me a spec'ed to max one and its damn good.
You can find lower spec'ed ones (still infinitely faster than a nc20 or dv2) for around £500 if you know where to look. Advantages this has:
*All metal body
*14.1" LED screen (with light sensor)
*A proper big boy CPU
*Easy to get to 4gb ram (both the dv2 and nc20 will need a single 4gb dimm, very expensive)
*Full size illuminated keyboard (very cool)
*Looks the business
*Proper discreet gfx chip if you want one