When priority for wheelchair users actually means first come first served

Brittany Ferries stated policy on their website is that wheelchair users get priority for booking the very limited number of accessible cabins available on their ships, though people with other disabilities may also book subject to the proviso that they may be asked to move to a different cabin. We live in the West Country and the family home is on the west coast of France, so realistically, Brittany are our only ferry option.
Their actual policy is that whoever books the cabin first gets it, regardless of whether they have any disability at all. Since the accessible cabins are known to be bigger than standard ones and they're usually at least £10 cheaper, guess what happens? I've actually had one couple complain to my face that I had taken their preferred cabin, the nice big one next to the lift that's really cheap. Whilst they could have had hidden disabilities, they didn't appear disabled walking up the stairs when the lift took too long to arrive, certainly weren't in wheelchairs and didn't have a disabled sticker on their car, and had not a clue as to why them taking one of the only two accessible cabins on that particular ship might be a problem.
Cruise ships have been insisting on proof of need before allocating accessible cabins for years because of this same problem. Whilst I'm not keen on having to prove my disability to anyone, trying to book ferry crossings with a cabin I can use is getting frustrating to say the least. We usually book well in advance, but even then accessible cabins can be hard to find and booking well in advance isn't always possible, especially at the moment.
It isn't difficult to work out that on most crossings (we do approximately 10 a year) there are only 2 wheelchair users on board at most because wheelchair users get their own separate queue for boarding (even apart from the rest of the 'disabled' travellers) and a big sticker on their car so that they're easily identifiable by the boarding staff. In many cases however, all the accessible cabins have been taken and we're stuck sitting in the often very noisy and crowded bar for the entire crossing because I don't fit anywhere else. On overnight crossings we have to book an ordinary cabin and I then have to negotiate very narrow corridors whilst other passengers wait in side aisles for me to pass (or try to step over me, thankfully not so many of them), my poor husband has to fold and lug the chair around because it won't go through the door, and I have to drag myself over quite a deep step to get into the bathroom, fortunately provided with plenty of handrails for when it's a bit rough.
The Equality Act still doesn't apply to ferries, if it did I'd be arguing with Brittany that what they're doing amounts to the same thing as allowing a pushchair to occupy the wheelchair space on a bus. The pushchair could be folded and moved elsewhere but the wheelchair user has no choice about where they sit so denying them that space amounts to denying them travel.
Sorry about the rant, in these times I'm sure people have much more important things to worry about, but I'm cross because they've done it again and their staff won't even consider asking non-wheelchair users to move to an alternative cabin if they can and there are no accessible cabins for three weeks before we needed to travel (for a previously postponed family wedding) so we're going to miss it.