Q: Long pronounciation of vowels is characteristic of Southern English, sometimes called Received Pronunciation, short vowels of Northern English. Those who feel that "proper" English requires long vowels would pronounce "says" as written (not "sahs" which doesn't sound any kind of English): "sez" is closer to normal use. There is a tendency to extend the length of the vowel by those wishing to accentuate their superiority. These people are known as "Rahs" for fairly obvious reasons.

BBC English is basically Received Pronunciation without the more extreme habits. Perhaps it would use "sayz" - definitely a z sound at the end, but that is normal in English with words ending in s.