I have a 28ft grafter pole, you could use this sort of pole like you are saying.
It is in 6 sections, but you could remove 2 of the sections to make it about an 18ft, and just slide them others on when needed. You would probably need to put a rubber end cap on the bottom.
I paid £203 for this pole and imo its a good pole, folds down nice and small.
When I bought it, it was a toss up between this and an extel pole which was about the same price. I'm not sure if you can remove individual sections on the extel though.