The same goes for any night ultra, but if it's cold at night try and be quick through any indoor aid stations (of which there are quite a few on TP). You don't need to stop for long to really feel the cold when you go back out and if you're down to a shuffle then it's hard to get warm again. I was on CP duty at Whitchurch last year and it was carnage with the number of drops. Quite a few left and came back 5 mins later shivering.
Sticking with that, recognise that this is what's happening when you do start shivering after an indoor CP and keep moving, you *will* warm up again within 5 mins if you can keep the effort going. Don't let your brian use the shivering as a way of talking you into dropping!
I reckon you should seek advice from a professional rather than asking strangers on the internet. You've got no idea who anybody on here is or what their experience is, nor do they know much about your background. It's too easy to follow the advice you like the sound of but really you've got no idea if that's going to be suitable for you. Completing the challenge obviously means a lot to you, so spending whatever on a consultation with a personal trainer has got to be money well spent.
I would echo what Peronel said, spend the next few months finding answers to those questions and you'll be giving yourself the best chance. In addition to that I'd say you need to get your VO2 max as high as you can, being physically fit will make it so much easier. You really want to avoid injury too though so do lots of different things (gym?) rather than just fast running. Again, a PT will know much more about this and should be able to give you a plan to follow.
Range of distances with 115k/+6800m being the big one. It's not had the publicity or big name sponsorship of the two mentioned in this thread but looks every bit as good, and means you might actually get to run some of it too (rather than the conga lines of Transvulcania).
I'm gonna see how the UTMB ballot goes and make a decision after that, looks like a great race though.
Cheers for the Etna link DE, I'll be sure to check that out too.