Really interesting observations! As British-Nigerian artists spending the bulk of our time in Britain as we do, we have inevitably developed a different ear and a very different humour, which (whether the African Centre audience like it or not) has led to the diversification of Nigerian stories. There is a danger of the accent (or anxieties about the authenticity of the accent) taking over from telling a good story. While the accent is an important part of the character and care has to be taken to avoid stereotyping or being taken as a British woman doing a bad parody, I do think that it is important to just tell the story that you want to tell. After all, this is your interpretation of one Nigerian woman. Refinement of the accent will not necessarily change the story that you wish to tell.