Hi Rory, I don't think this is a Kalanchoe, because of the tiny pin sized markings on the leaves. The one plant that has these is Crassula. This plant is one of the most often bought to start a collection, but yours is a little unusual.
This one is a special variety of the Jade plant, and goes by the name of Crassula ovata 'Ripple Jade'. You can see more about that particular cultivar here, and more about how to grow Crassula here.