I agree with some of the above, having something to fall back on is important? but is plumbing what you really want to do?
Perhaps you are discounting University too soon because your thinking about getting into flying asap and 3/4 years at uni is too long. I know that feeling I was there 3 years ago, but here I am at uni, loving it and it's probably the most valuable experience I have had, let along it gives me something to fall back on.