Vivienne,
Cth works for me
I have a few catt alliance I still don't have names for I might have to wait for the flower, even then it might not be the right one. Even two flowers from 2 different plants of the same cross can look different I still don't know if I'll ever identify them correctly.
I'm not an expert in catts, but long and thin pseudobulbs that I have usually have Brassia traits in them..long slender leaves come from epi. (encyclia) or leilae but I'm not that possitive to go ahead and tell you that's the case for your plant. And that's still too broad.. Maybe some other geeks will know..
Good luck