ˈθʌrə is standard in British English. Likewise "borough" is ˈbʌrə in British English and ˈbʌrow in American English. "Edinburgh" is ˈɛdɪnbʌrə / ˈɛdɪmbrə in British English, and Wiktionary says this is the American pronunciation too, but I've definitely heard American say ˈɛdɪnbʌrow.