I was in Tesco's yesterday and saw a mini LED head torch for £8, never one to miss a chance of a new toy I got myself one. It takes 3 AAA batteries and has 4 White and 3 Red LED's. There's a single switch on top and you cycle through 2 x White, 4 x White and 3 x Red. There's a small rubber seal around the battery compartment so all in all it's pretty good. One thing I don't like is that it cycles through both white LED options before it switches to red, I would have thought switching Red 1st would be the logical progression.
So, today I was in B&Q and while waiting at the till I saw another small LED head torch, this one by Energizer and costing £7.95. It also had a Red/White option. Again it's 3 x AAA but only has 2 x white LED's and 1 x Red, however it has a 2 way slider switch that allows you to select either Red or White. That's a better option IMO but unfortunately it probably isn't as well sealed as the Tesco one.
Trying them outside it seems the Energizer is just as bright with 2 x LEDs as the Tesco one is with 4 so all good them. For the weight conscious, the Tesco one is 87g, the Energizer 77g.