Hi....I have a similar questions at all!! My teacher said that to get a good grade its important that you sound like the character and that you are subtle (I'm not, unfortunately). Instead of saying:
"I hate Eva for using my name. How rude of her!" it should be more like, "The impertinence of the girl! How dare she use my name?" (Mrs Birling's thoughts about Eva) This is just an example and not that good, like I said I'm not very good at doing 'Imagine you are' question. I'm just gonna skip that one in the exam and do the other option instead.
...Hope this helps