From what I could find, the ringtail and the cacomistle are two different species of the genus Bassariscus, B. astutus and B. sumichrasti respectively, the latter having a more southern natural range.
According to Zootierliste only the ringtail, B. astutus, is currently represented in European zoos, and the individuals at Exmoor should be of that species.
So it would seem the use of cacomistle is erroneous.