http://www.dealextreme.com/p/mj-808e-ha ... 8650-57100
Same as that UK store, so buy it from DX. It looks good to me, you could run two of them..
There are two versions of that light for sale on DX. The basics are SSC P7 leds are some of the brighest but hot and high(er) on energy consumption. Usually has a very wide floody beam.
XM-L is a newer LED pretty much as bright but a lot cooler and lower on consumption. Naturally a slightly narrower beam but usually a nice hot spot and enough flood.
Based on calculations and my experience with four good quality 18650 batteries they should produce the quoted 3-4 hours, maybe a little more. My torches with single batteries last 40-60 mins.
97 GT LTS-1
99 GT Lobo DH 1000 x 2