this is why I start with GL
http://susangarrettdogagility.com/2010/09/head-halters-vs-a-flat-buckle-collar/
I've been having a long, hard think and this may just be the approach for Darla. I will have a go at following what the article says, about turning her head towards me, showing her what I expect of her. It's highly likely she just hasn't a clue what I expect from her in high distraction areas. I will also bring out something yummy for her for reinforcement (she is generally a lot calmer on the GL so she may be interested).
I was reluctant at first to use the GL as I thought it forced the dog to do what you want and not teach it. But obviously it can be used as a fantastic training tool to calm them down enough so they have a chance to listen and learn from you, thus removing the need for a GL when they know what is expected of them.
Thanks very much all for the flash of insight, I will keep you updated on our progress!

like what are you going to do for your next trick mommy