Courses for learning RP:
https://receivedpronunciation.thinkific.com/collections
https://speakbritishenglish.thinkific.com/courses/the-vowels-of-british-english?ref=376ffa
Wikipedia materials:
https://en.wikipedia.org/wiki/International_Phonetic_Alphabet
https://en.wikipedia.org/wiki/Received_Pronunciation
https://en.wikipedia.org/wiki/IPA_vowel_chart_with_audio
https://en.wikipedia.org/wiki/IPA_pulmonic_consonant_chart_with_audio
https://en.wikipedia.org/wiki/Airstream_mechanism
