I just bought an Acer 1810TZ. I paid around £360, but thy are normally £400-450.
There is a clear distinction between ultra portable laptops (as my Acer is) and Netbooks.
Netbooks have an Atom CPU (or as with that Lenovo, the AMD "Neo" equivalent), and are massively underpowered for anything aside from basic computer use.
My Acer has a dual core CULV Pentium U4100, 3GB of ram, a good 250GB HD etc. Its no speed freak, but it can handle any HD content I have tried, as well as light 3D graphics (the inbuilt Intel graphics isn't the best).
The battery though is genuinely good for 8 hours! Most Netbooks wont reach that!
If its a true netbook you want, then the Asus 1201n is around £400 and has a dual core Atom 330, 2gb of ram, the NVIDIA ION chipset and a 12.1" TFT, battery is supposedly good for between 3 and 5 hours.
I can heartily recommend the Acer though, its very nice. Though that Lenovo will be too, I'm sure, though it seems heavily over-priced for what it is...