Ian,
Since you're a 'senior window cleaner' (that's a euphimism for 'coffin dodger'

), I'd love to hear your opinion of it.
Use it for a couple of days first though.
I've used a similiar pole to Cleantechs, and I guarantee you'll love the difference; though I'm not offering you a money-back guarantee like I did with Gazza.
However, I'm not sure what you mean by 24' pole plus conversion bits? The Zensor will give you a tough lightweight pole for £20 that's 15 foot long. If you buy two Zensors, then you'll have loads of spare sections (but I don't think they're needed; I've been abusing mine, and it's great) and can use the two bottom sections of your spare poles to give you an extra 3 foot; therefore an 18 foot pole.
But 15 foot is long enough for most routine two-story work.
However, for about £65 you can buy an 11 meter Gangster; which would give you about 23 foot of pole (you can add sections from the Zensor to get you to 27 feet); but I'm still out on how robust this is. I think it'll be fine for normal three-story work, as long as you don't have anything too extreme (such as using it at acute angles).
I use my DIY Gangster on Friday; so will post about it then.