I've popped in to say Hi from the other thread.
There is a solution to this, but I'm afraid it requires Apple's intervention.
If you are suffering the problem, I suggest phoning Applecare - you should get escalated quickly to a Level 2 support person, who will inevitably have to send the problem off to the Apple engineers to sort on your behalf.
By all means head over to the other thread to see the process they took me through, but like I say, it's not something you're going to solve yourself.
That's what my engineer did to my account too. And he sees the exact opposite of what all my devices show me as myiCloud storage status. ie. I see 1.5 GB of 25 GB available, he sees 23.5 GB of 25 GB available. Very strange. Sent him screen grabs to prove I wasn't making things up but no heard anything since …