Well, two points to start off with. The Cullan Bryant, Dmitry Rachmanov Beethoven and his teachers double CD may be had from hmv.com for £6.99 at the moment, and the claim that the Gary Cooper Diabellis (£10.99 from the same source) are the first to present them as they might have sounded when written has only partly been addressed. What about the superb recording by Paul Komen? Oh, and well before that, Jorg Demus recorded them, plus over 30 of the other Diabelli variations, for Archiv. I still have the double LP album, (sadly in very poor condition). I do wish Universal would issue those on CD.
Oh, and I half expect a commercial recording from Andreas Staier before too long. He toured it last year, including performances in Prague and our own Lake Disctrict using a fortepiano. I have not been able to find which model, however. The Prague performance was broadcast and there is a decent mp3 available. Staier too included a selection of other composers' Diabelli variations, though far fewer than Demus recorded for Archiv.