Are Idioms Metaphors?

First off, I totally agree with Lakoff and Johnson, metaphors are everywhere. They've become engrained in our culture and speech, we can't escape them. That's fine though, they make conversations more interesting. However, as I read "Metaphors We Live By" it brought up the questions, "Are idioms actually metaphors?" The OED defines metaphor as "A figure of speech in which a name or descriptive word or phrase is transferred to an object or action different from, but analogous to, that to which it is literally applicable; an instance of this, a metaphorical expression."

What I get from Lakoff and Johnson's definition is that Metaphor is pervasive in everyday life, is not just characteristic of language alone, but also of  thought or action as well. Our ordinary conceptual system, in terms of which we both think and act, is fundamentally metaphorical in nature. "This is what we mean when we say that the human conceptual system is metaphorically structured and defined. Metaphors as linguistic expressions are possible precisely because there are metaphors in a person's conceptual system."

Back to idioms though. Aren't idioms linguistic expressions? Aren't they somehow similar to to metaphors that are linked to a person's conceptual system? The OED defines idiom as "the specific character or individuality of a language; the manner of expression considered natural to or distinctive of a language; a language's distinctive phraseology." Are idioms just what Michael Reddy calls a conduit metaphor? He says that,

IDEAS (OF MEANINGS) ARE OBJECTS.

LINGUISTIC EXPRESSIONS ARE CONTAINERS.

COMMUNICATION IS SENDING

So for example, let's take the idiom, "Not for all the tea in China." The idea of "I wouldn't do that for anything" is based upon the object tea. The idiom itself is a linguistic expression, and thus a container for knowledge. When you speak/communicate this idiom, you are sending a message. So doesn't that make this particular idiom a conduit metaphor? Is idiom a metaphor for "meaning another meaning?"

I also want to mention "Orientational Metaphors." "But there is another kind of metaphorical concept, one that does not structure one concept in terms of another but instead organizes a whole system of concepts with respect to one another. We will call these orientational metaphors, since most of them have to do with spatial orientation: up-down, in-out, front-back, on-off, deep-shallow, central-peripheral. These spatial orientations arise from the fact that we have bodies of the sort we have and that they function as they do in our physical environment".  They have a basis in our physical and cultural experience. Though the polar oppositions up-down,in-out, etc., are physical in nature, the orientational metaphors based on them vary from culture to culture."

So what I'm trying to grasp is 1) Are idioms metaphors? and 2) Are the meanings of idioms and metaphors mostly rooted in location, or the location of the speaker? Both? As in, some countries have idioms that don't make any sense in other cultures. Or, for a metaphor. "Sit in the apple-juice seat" The understanding of that metaphor is based on the location of the person standing near the table. Are the meanings of metaphor and idiom just based more on a cultural, native language, or locational standpoint?