Bocks have arrived! Yeah!
I've had an hour or so's totter around on them. Was walking unaided (mostly) after about 10 minutes. It does occur to me though, that the problem with learning to stand up on them is that you already have to be fairly confident with your balance, or otherwise you'll get upright and end up coming straight back down again ...
... could be wrong, haven't tried it yet, but I'm going to have a more in-depth explore of what they'll do tomorrow :-)