In reply to The Bantam: It really depends what you're going to use it for. I've had a tikka XP for a few years and it's been great, just about powerful enough on new batteries to run on difficult ground. The Vicar's comments about petzl being unreliable are unusual, there have been plenty problems with the myo XP but apart from that they have a decent reputation. I've certainly abused mine and it's still going well. It's also one of the few products that never seem to get returned faulty to the shop (apart from the myo XP!).
If your running on non-technical terrain a self contained torch will be adequate and more reliable than one with a separate battery pack. There's plenty out there to look at, the most prominent being from BD, petzl and silva and all good.
If you want something for more technical terrain the more powerful torches come with a remote battery pack (either at the back of the head or loose), the silva trail runner is good value, also the petzl RXP and black diamond icon are popular.
There's loads of information about, you can't really go wrong with most of the decent brands these days.
Ben