Thats right.
NO DH, ergo an Alert Height.
If you have a DH of 50ft you don't have an Alert Height as you are operating to Cat 3a.
Cokeman, I stand corrected Cat3C has been removed from EU Ops. It now lists only 3a, DH less than 100ft and 200m and 3b, less than 50ft, or no DH, and 75m with fail operational system, which is where Alert Height comes in.