As I was a little doubtful about the cotyledon suggestion - but am an utter ignoramus about succulents, as I confess to being about most things except lily species and perhaps cyclamens - I asked Rhoda McMaster, the South African native plants guru, to have a look at this thread for us. This is what she says:
I think this looks more like a Kalanchoe - maybe tetraphylla (syn. thyrsiflora). One would have to wait till it flowers. It cerainly does not look like a Cotyledon
If that's right, Daisy, it shouldn't get too big, not much more than a couple of feet, and kalanchoes anyway like being underpotted.
