Steve, I wouldn't know if the action is altered with the extension fitted, but the whole point about these rods is the zero lock-up. I suspect these rods have a similar action to the more expensive rods by Carbotec.
I phoned around for some prices for the 14 footer and found that Davies Angling in Staines, Middx were selling them for ?149.99.(RRP ?210).
The RRP for the 15/17 float rod is ?225.00 so I reckon they could do this rod for about ?160.
Why not give them a ring (0800 136 031) and ask?
Sorry, but I've chucked out the A T review on these rods, but remember reading that these rods are supposed to be the dogs doohdahs.
Let us know how you get on.