People have different opinions about this, but this is my position: “nontheistic” is not used as synonym or euphemism for “atheistic.” The atheist, like the theist, takes a definite position with respect to the doctrine that God exists. The atheist denies or disbelieves it. The theist affirms it. As nontheistic religion is defined, the prefix “non” should be understood to mean simply that the theistic reference does not apply. Ours is a religion or belief of a totally different type in which the God question is not of primary concern, however we embrace the other defining features of religion such as a shared set of values, history, traditions, culture, aesthetic and community. While the atheist seeks to reject all religion, we seek to redefine the popular concept of what religion means within the public sphere.

I see what you are saying in regards to witches, however, remember that historically speaking witches are viewed as the “handmaidens of Satan,” essentially in servitude to him. So from that standpoint we’re really just splitting hairs. The witch is/was viewed as Satanic. There’s an entire wormhole we could get into regarding the gendered distinction of "the witch" but let’s save that for another time.

I support your proposal for a Satanic movement in the UK. Onward!