Neil, that kind of exploration and discovery is one of the things that keeps all of us coming back for more. And if you want to claim it as your personal discovery, why not?

Now that M.Ted and I have gotten beyond our little disagreement, I'd like to offer another suggestion that is so basic it almost seems that it isn't worth mentioning. My suggestion: just try tossing things in (when you're playing by yourself), and see what happens. For example, if you're sitting in your room strumming away at your I-IV-V stuff in the key of G (G-C-D), try tossing in one of the I-IV-V chords from another key, just to see what it sounds like; throw in an E, an A, a B, an F, or whatever strikes your fancy. Play with major and minor variations, different inversions, etc. If it sounds awful, there's no harm done; you're just trying it on for size, in the privacy of your own home. But chances are that your experiment will sound suspiciously like something you may have heard before, and you will start to recognize other progressions and patterns beyond those that are instantly familiar to you. They call it "playing" music, after all; and the joy of discovery is one of the things that makes music so much fun.

I'll bet even M.Ted agrees with me on this.