You will need to locate the SSID within the hierarchy configuration and then remove it at that group level. For example, if the SSID was created at MD\Corp\UK then you need to delete it here.
If you are not sure at which group level the configuration was entered, use the following command to understand this:
show configuration effective detail
From the last line, it sounds as if you are making the changes on the Mobility Controller. You will need to login to the Mobility Master, locate the configuration and then remove. This in turn will remove it from the Mobility Controller.