good call, they offer 64 bit (bonus for vista) and offer performance increase for the same battery consumption. (form memory around 15%)
from what i've read the price difference should be closer to the £50 mark rather than 100. Pricing shoiuld be announced on the 28th, anyone who breaks the nda before is unlikely to get stock.
if you can't wait though, core duo is still a very capable chip.
the pegasus 660 is the duo, the pegasus 665 is the duo 2. (not sure if I can link to laptop suppliers?
ALso warranty is important to consider on a £1k laptop, some suppliers offer 3 years as standard, some offer 1 year then can cost between 1-200 pounds for a further 2 years.