Barrier of "tumult" during meditation Could someone help me understand, or at least name, a phenomenon which may be standing in the way of meditative practice. It is so hard to express that I'm at a loss to know where to begin to seek help.

It could perhaps be best expressed as a sudden tumult of sensation (mainly voices and images), like a confused radio or instrument panel on an aircraft struck by lightning. It is almost impossible to comprehend its contents and, sadly, like with very sudden external noises, and the like, jolts me out of practice such that it suddenly irretrievably ends the session. It has no fixed emotional or intellectual content, but is nevertheless strongly emotional and intellectual in an unfixed way, like the sea is strong but fluid. It is not a somatic (body) sensation (ie not tingling, or whatever), but one of the mind. I suppose if pushed, many images include people I love, but that is a tiny part. It is draining.

It begins some time after I transfer from a meditating for calm and emptiness (which is familiar and which I've practised for years, principally through concentration, mindfulness, non-clinging to thoughts and images, awareness of body, etc) into noticing and contemplating the way things are per se, without objective beyond understanding (ie no for).

I'm interested in the scholarship of religion (a theology geek) and so have taken time to understand, intellectually, the ideas behind Buddhist practice, along with many other religions, without any real sense of membership.

But it's only recently that I've begun to consider these in the context of meditation (ie the thing rather than the idea).

I would be interested to know what this is, what the right thing to do with it is in order that I could proceed with meditation, ideally not dropping out of it whenever it happens. Does it help to keep a structure to this form of meditation rather than drifting to it from intellectual knowledge and a calmed state?

If it has a name that I could look for it in books, etc, that would be particularly useful.
I won't try to guess exactly what you're experiencing, but one thing that trips people up a lot is the expectation that meditation is a one-way road to greater and greater calm. In reality, there's an initial calming, followed by the emergence of various kinds of experiences at other layers of the mind, some of which are pleasant or orderly, some of which aren't.

One thing that Buddhism teaches is that the mind is a sixth sense alongside vision, hearing, touch, taste, and smell. This means that thoughts and mental imagery are on the same level as sights and sounds- they are data that enters through "your" doors of perception from "outside". They don't belong to you and are largely out of your control. 

This is contrary to our usual Cartesian model of thinking that our Thoughts are the expression of our core Self, and it's also contrary to the common idea of meditation as the conscious quieting of all thoughts. 

I only have my own experience to go on, but I believe that the ability to achieve a complete stilling of the roiling, random soup of images in our minds is very very rare, if it exists at all, and not a requisite for good practice.