Leo Andrew was Korberg's understudy in the first cast. Siobhan McCarthy took over from EP when she left, the men stayed for a while IIRC. Michael Howe played Freddie at some point before EP and Korberg left, and Grianne I think replaced McCarthy as Svetlana, along with Peter Karrie as Freddie.
The final cast had Grianne Reniham -Florence David Burt - Anatoly Anthony Stewart Head - Freddy Ria Jones - Svetlana/Florence Understudy