I have added a few more steps to the scene and started working on the face. I can see that there is one step in this that is particularly dodgy - the first step backwards. I tried to block these few steps out more sparingly, but I think it would have been better to have at least one more key pose in there while I was blocking out. I will try and find a balance between adding too many frames right away, and not enough.
For the face I have just started with the first word, to get to see how the rig looks in action. I did also start adding a jaw bounce for the second word, but I think I have over done that. From this point I will go through and do the jaw bounce and work on blocking out the facial animation, rather than going right in with details.
I've had a few glitches, but nothing too big. The one below just seems to appear when I move frames around, and goes away easily enough when I carry on working.