Hi Ian,
I am sorry that the anxiety caught you off guard...that is a dirty trick;(
This is common however. Just as you start to get a handle on managing the daytime anxiety....often the nocturnal attacks will strike.
The good news is that you can use the same tools to deal with these night time panic episodes, as you have in the past.
Postivie mantras, breathing and progressive muscle relaxation are going to be powerful defense skills for you.
Here is the link for some of these, in case you need to refresh on them.
http://www.stress-relief-exercises.com/
Keep up the good work. This is not a setback...just a small detour. Keep posting and let us know how you are doing soon.:)
S.C.