You don't need a head lamp. Any reasonably bright light mounted on your handlebars, and aimed at the ground about 2 bike lengths in front of you, will be sufficient to show bumps on the ground and low hanging branches. Too many cyclists don't use head lamps properly, and end up shining them directly at oncoming people's faces.
Totally agree. I have a couple of these handy
https://www.7dayshop.com/products/7...led-flashlight-with-mount-silver-ring-DS-002S
They're cheap and cheerful enough to equip a couple of bikes, and used as torches as well. You can get spare mounts and o-rings from the same source, also some cheapo rear lamps that are very bright and again, cheap enough to keep a spare or two. Useful if you have a more than one bike and don't want to spend a fortune!!
I also have an Aldi font light from a set I bought a few months ago, this happily lights up the road a couple of bus lengths ahead, plus to be seen from way off especially in the weather we are having at the moment I've ordered a Cateye Omni 5, which hopefully will be strong enough to do the job without clobbering the vision of oncoming drivers/cycists/walkers etc. . And a spare mount for bike 2.
A helmet lamp is useful if you come off the bike at night and want to be seen rather than run over (something the "I'm going to wear black clothing" brigade seem to forget), or if you are stopping and want to see where you are putting your feet on a footpath-free lane - you don't want to step into a ditch or a dollop of what horses leave behind! But you don't need a retina-burner for that.
The other thing is, all my lamps will run on AAA or AA batteries so keeping spares becomes simpler, and less fiddly than messing with button batteries on a cold, dark ride!
PS 5/11/20156 - removed reference to previous post - wrong forum