http://www.torchythebatteryboy.com/
Lots on here about the batteries required for the xm-l t6 light and which are the best ones, he also sells the better makes on his ebay site – http://myworld.ebay.co.uk/big_f_d_d?_trksid=p2047675.l2559
Not sure if he is just bigging up the one’s he sells but looks good enough for me.
Also on that site is a really good test of a whole heap of bike lights.
Took a punt on one myself off this guy since he is based in the UK.
Does not come with batteries though.
http://www.ebay.co.uk/itm/251091020942?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
Not got it yet but quite keen to see how they perform for such a cheap price.