Thanks for all your replies and suggestions.
I tend to use a soft bag when traveling, so there is not much hope of getting the spars in there.
I have taken the spars as hand luggage in a clear polythene sleeve, and security were OK about them. However, I was more worried that the budget airline staff were going to pull me over and demand payment for oversize luggage.
Anyway, I ended up getting some Xxxxx P300 tubes, and ferrules, and cutting them to size with my Dremel. I am no expert (significant understatement), so I can't really say how they compare with the real thing, but they did take my vented 1.5 aloft in a 15 mph breeze.
BTW. How do you get them out of the leading edge ? Next time I am thinking that I will send a piece of string through with the first section so that I can use it to drag the whole lot out when I have finished flying, or maybe I will tape the pairs of sections together, so that while I am away i just treat them like normal spars.
All the best