I've looked at the Brodex website and they don't say anything about measuring the pole height from the waist. What a load of BS.
If I was buying a pole of off their site I would think like you did that a 31ft pole would indeed measure 31ft. And not 28,29 or 30ft.
I agree that this is misselling.

Print off a copy of the Brodex webpage with the product and price, then get in touch with them and see what they say.
If they don't wanna oblige I believe you have a case for Trading Standards, but make sure you have the evidence first (just incase they change the information on the webpage)!
