From what I've heard it's worth every penny. Surely just to say you had the Margaret Curtis Tour is worth sploshing out £30! The more time goes by the more I reckon I'll never have the chance.

One thing I do know, even if it's only Callanish I then you'll learn things that you won't find out if you're on your own. I mean you could get a good book and stand there with a diagram going "is it that one or that one?" whilst pointing aimlessly etc ... but it ain't the same is it!?