On-One / Planet X bikes and components

My first carbon bike and I'm not sure about how good carbon is to being abused.

Very good, in my experience. I've killed steel and Ali frames before. Never carbon. Well, not yet.

As for Ti, welding that stuff is very difficult and never sure that it is done properly.

It's really not. You have to back purge it, but that's about having the correct fixtures. Welding Aluminium is far, far harder.

Is the pipework still aviation fuel line?

Never was, as far as I know. Most decent Ti frames use butted tubing, and I can't imagine that aviation fuel lines ever used butted tubing.