Just an update that I purchased off ebay and it came new in the box, with hub and I've got as far as setting up the hub without any issues. Now to source 4 C batteries... Also, installation in a glass door is much more expensive than the product itself!
That is a good deal then, haven't seen it that cheap.
Says it comes with the hub: https://www.ebay.co.uk/itm/SureFlap-Microchip-Pet-Door-Connect-with-Hub-BRAND-NEW-BOXED/293381005425?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
He also arches his back and hisses/screams (?Not sure of proper term) at thin air though. Like he's squaring up to a ghost cat. (fierce)
Your cat is perfectly healthy in that case. That is what all cats do (y)