Greetings Gill,
I have several headlamps and have owned a bunch more from the cheeps to expensives. Not sure off my head the adjustable focus part. That may be difficult to find??? But one of the more experienced fellows may be able to guide you in that direction.
But two of the lights I have that I love are: Nitecore HC90. Mine is the vn model. It is my absolute hands down bar none favorite headlamp I have ever owned. I will give you a link. This light made me retire my other ones. It runs on a single 18650 protected button top cell.
http://www.candlepowerforums.com/vb/showthread.php?386085-HC90vn-The-Best-Headlamp
My other lamp I like is: Fenix HP25. Its not the brightest or floodiest, or throwiest, but for me it does everything WELL! Oh and it does run off of AA's! And that is swell at times too.
I am going to subscribe to this and see what some of the pros have to say.
Welcome to the forum and good luck.