Hi Micio, hope you're well. I understand what the plant is now and have to say that I had imagined it to be slightly larger when you mentioned that the leaves were the size of a rubber plant. If you like these little plants that grow in old walls etc then have a look at the sedums, like sedum rupestre, as they're really fun and grow VERY easily- just like saxifragas

Hi bubbles, good to see you're still gardening away! Ok, for fountains I would suggest hostas and ferns at the base, which highlight the presence of water and plants like Zantadeschia aethopica 'Crowsborough hill', Iris pseudocorous and then dwarf water lillies (depending if you have the space) in the water of the fountain itself. Let me know if this is the kind of thing that you had in mind and I can elaborate...
Ciao...