and seem to have active and passive noise cancelling technology (unless that
is an exaggeration for something which doesnt work?)

Passive noise cancelling: They get in the way of other sounds. Most
headphones will do that to some degree, some more and some less.

Active is the "listen and counteract" thing. That works for some sounds
(machinery) better than others. I have a friend who was an early adopter
of Bose's entry in that field and loves it; my experiments with cheaper
knock-offs have been in conclusive (they definitely make a random-noise
environment such as a shopping mall sound _different_ but I'm not
convinced they actually make it less distracting).

Haven't checked the eBay link so I have no opinion about that particular
unit.