[Closed] What light for...

Petzl e [emergency] light.
Adjustable band fit antwhere, solid and flashing white and red light. Full power not greatest but if its an emergency it does ok. Nice little case to protect it whilst in the bottom of your bag included. Mine is always in there.
Try ebay.

Actually just re read your post, its prob not bright enough!
Nice bit of kit all the same.

small 3 w led torch and cable ties. Available from multiple sources for much cheapness

Ditto TJ

One of [url= http://www.aldi.co.uk/uk/html/offers/special_buys3_15768.htm ]these[/url] maybe, and a 2fish lockblock.

That looks perfect if it has a decent mount that I don't have to leave on, and if I can ride off-road by it...

One of these or similar
high mode for off road, low for on

http://www.bestofferbuy.com/mte-m2-cree-q5-2mode-150lumen-led-flashlight-3aaa-p-53139.html

Velcro attachement only

http://www.fenixtorch.co.uk/led_torches/lockblock.html

Whether you could ride offroad with it entirely depends on what/how you want to ride I imagine!

If you can wait a couple of weeks, then I've just bought this helmet light setup and it looks fantastic...

http://www.dealextreme.com/details.dx/sku.15335
http://www.dealextreme.com/details.dx/sku.6105
http://www.dealextreme.com/details.dx/sku.12000
http://www.dealextreme.com/details.dx/sku.20392
http://www.dealextreme.com/details.dx/sku.2709

But I guess it's more complex than just keeping that Aldi torch and a couple of Duracells in your bag.

Easily enough to ride offroad by though.

Velcro attachement only

http://www.fenixtorch.co.uk/led_torches/lockblock.html

Those lockblockie connectors are also available from the Chinese sites for around a quid a pop
They're rubbery

The £4 ebay light isn't bad, stick some decent alkalines in it for emergencies or some decent rechargables (not the super high capacity but go flat on a shelf ones) if you plan on using it more than once.

Lasts about an hour on 3x 1100mah AAA's