Deathtrap at The Mill at Sonning until March 30 Review by DEREK ANSELL TO begin with, Deathtrap by Ira Levin has more twists than an elongated corkscrew. A once successful playwright has hit a writing block and is envious of a brilliant play, written by a young student who has sent it to him. He seriously considers inviting the young man over and murdering him before claiming the play as his own and making a fortune from it. Now that is just for starters in the first 10 minutes. Nick Waring, as author Sidney Bruhl, played him as bitter, sarcastic and witty but cruel, so that you believed he co…