When I meditate, I find that when I let go of the mind, the breathing, the need to try and visualise/hear everything, there is a gateway stage/level of meditation. It is the very first altered state of conciousness that I can enter.

I like to think of it as a spring board; from which you can go higher, but does this idea exist outside of my head in Yoga (i've ordered a book from amazon!) or any other discipline?

does it have a name?

One of the very first points Patanjali speaks of is the need to have an anchor or point of focus in the growth of expanding consciousness.
He specifically states that without guidance the mind follows interpretations of altered states as landmarks to expanding consciousness.
Moods, the thoughts of nothing or exalted experiences, etc. These are not the anchor he speaks of for these things do nothing to expand the awareness or consciousness permanently. Only the awareness of the absolute and the continued focus on that expands consciousness permanently.
The proper tools, guidance and one pointed focus are all that is required.
Even then, the habit to look for landmarks to gauge the progress is a bad habit, for the mind in its projection of what enlightenment is and what the hallmarks of enlightenment are distracts the mind and steers the course towards illusion.
 Here is when the experienced teacher guides the not always so willing student who wants instant gratification to focus again on the absolute and not the projection of the goal.

It's a good job i've started reading his sutras then, eh?

One thing that bothers me a little, i keep seeing the words Dangerous, and Warning with respect to meditation. What's that about?

I was reading about puritans whom try to stop bad thoughts from entering their heads, when they do, the puritans can't hack it, and run of to commit suicide. Is this the danger, or is it something else?

I don't know what you are reading.
There are different interpretations of religion, the Bible, the Upanishads, The Baghavad Gita, and The Yoga Sutras of Patanjali.

The level of consciousness that is involved in the translation of the original scriptures plays a key role to interpretation and the passing on of knowledge in its purity from one to another.

The words are irrelevant for the nature of any teaching is the essence behind the words.

It is dangerous for man to ignore God for it produces suffering. Suffering meaning duality, sickness, happiness with sadness. dangerous meaning that in the language that is used and understood an adjective used to describewhat takes you further away from the realization of the divine nature within.

Warnings come from those that try to impress the fact that there are fast ways to self realize and there is the long way around the barn.

i guess its the long way for me.
but then i heard that there is utterly nothing to attain, so all this yoga discipline seems like a lotta hard work for nuttin.
veda's all about the strands of material nature anyway, so what the heck do i kno?

There is a lot of something in that nothing, and the strands are the strands that connect the manifest to the unmanifest, and the understanding of the point of conception and how it relates to you.

I think i have found the answer to my question:

QUOTE

does it have a name?

yes, its not actually a base state, but a state of being at one with nature. This is not what i want.

Patanjali says:

QUOTE

The practice of concentration on a single subject (or the use of one technique) is the best way to prevent the obstacles and their accompaniments.

Now that's more like it. AUM...