Hi John
I did think about Graptopetalum in particular and will have a more thorough search on the internet and through the books I have. I know there are crosses between Graptopetalum and Sedum too. The original plant was 3 or 4 times bigger and had been thrown out because it was presumably too big. In Rome it is very common for plants to be abandoned once they get to a certain size. It was almost destroyed by the -7°C of the previous winter whereas none of my other sedums batted an eyelid. That might suggest there is Graptopetalum in there. I have Graptopetalum paraguayense and some Echeveria plants. The latter have a more bell-shaped flower though. I am away in the UK for the next few days but when I get back I'll start to look deeper. Thanks.