It's important to note that these are phonemes, which are the smallest units of sound that differentiate meaning in a language. Some vowel sounds can be pronounced differently in different contexts, but they are still considered the same phoneme.
Here's a breakdown:
* Short Vowels: 5
* Long Vowels: 5
* Diphthongs: 8
* Triphthongs: 2
Let me know if you'd like a list of the specific vowel phonemes in RP!