I just posted some of my Ashes to Ashes theories on my journal. It's fairly comprehensive, a little bit sarcastic, and also, probably entirely wrong.
A note about spoilers: it will spoil you if you haven't watched BOTH next time trails that were shown at the end of 3x7.
If you're interested, you can find it
HERE. Be warned, I use very saucy language. AKA: I curse a lot.