The Hotelopia site offers very low rates for what I am looking at. That is via the 'public' Hotelopia webiste. No question of industry discount or anything else.

There are then various routes into the website, e.g. through Quidco with a smallish discount. Obviously the hotel is never going to ask for details of my Quidco membership, and why would the hotel even know about it ?

One of the routes into the Hotelopia website is through the BA Clubs gateway and that gives a 13% discount. The question I am now trying to get to the bottom of is whether the hotel (as opposed to Hotelopia) would ever want to check my entitlement to use that gateway; assuming the hotel even know I have used it. It would seem odd if the hotel did, although lhrtolgw's experiences might suggest that they would.