You know the problem is not always with the pet stores.
Often times it's consumers who are unwilling to pay for the bigger hutch / cage...which makes demand for the smaller / cheaper versions much greater.
You should see the faces on some customers when I try and talk them into getting a dog crate, or sourcing NIC cubes, or even using a shed, or making an indoor playpen. "We don't have the space" "It's too expensive" are just some of the replies. "THen don't buy the bunny and force them to live in crappy accomodation you moron" is what I'd love to respond.
If people emailed pet stores about the slemka storage cubes that B&Q currently have on order, and got them to stock them, along with examples of the brill condo's you can make, or other alternatives - maybe they's listen. You need to provide the pet stores with cheap alternatives I guess - that would be in demand.
Just my thoughts from working in a store.