Authentic dialogue

I want to be able to record a short piece of dialog, say 5 mins, convert it into text and then use the text to create a voice to use in my story. I’ve tried describing the dialogue style of one of my characters, Dave, as “a young man from the East End of London who is now trying to speak with a more refined accent”, but when I select a section of text and attempt to rewrite with the prompt “rewrite in the dialogue style of Dave” I get something sounding like Dick Van Dyke in Mary Poppins. Any suggestions?