In terms of pronouns it is a good rule of thumb to go by the gender of their dress. If someone is dressed like a woman then using female pronouns is appropriate. If someone is dressed like a man then likewise. Most trans people would greatly appreciate the correct use of pronouns as there have been reported scare stories of trans people people left in the street untreated, or treated less than well by emergency response staff because of their trans status. Many police forces will have an LGBT rep, I would hope that paramedics would have access to similar resources or people to advise in such situations.