I highly recommend Anne Walsh, Confidently Speaking UK Speech Coach, not only for accent reduction, but also dialogue coaching for auditions. She has a positive personality, very people-oriented.
For my accent correction, Anne identifies not only the individual sounds (mostly vowels, but also problematic consonants). The speech pattern is the ultimate giveaway. She has unusual words and phrases to describe these patterns which enable me to picture the problem so that I can correct it. She could easily write a book with her own original materials. She makes up new drills for me almost every lesson, and finds great practice material. She is well-read, has an extensive vocabulary plus a great sense of humour!
Though I had worked on speech extensively, having lived in the South growing up, casting people would ask frequently, “Where are you from?” a code for saying, “You have an accent.” I never had a problem speaking dialogue on film during a 15-year acting career. The difficulty was in regular conversation.
Marianne Mason Actress