So I found this:
Cultivation: Not easy; it has a large root and lives among rocks. This tropical cactus prefers loves warm, moist, humid conditions, and mist spraying is a must in summer. Water regularly during the growing season and use a very draining mineral potting substrate. At the onset of winter, do not water. Uebelmannias need heat all year round, and extra winter heat; minimum 10°C is best. Avoid any frost. Keep cool in summer. This plant proves to be root prone if kept too cold in winter. To help stop this, a good deep collar of pumice or lava grit is an excellent idea. It prefers a full sun position and possibly afternoon shade in summer. If you can place it so that this occurs, the plant will be much happier.
Propagation: By seeds. Germinating seeds can also be tricky. But plants are often grafted making them easier to grow, particularly through the winter. If possible, using a rootstock that is hardier than the Uebelmannia is the ideal.
Seems like finding a grafted one would be the safest bet!
