There is some good advice on preparing for the viva on the last page of the Accountability partners thread in this forum. If you don't already have a list of possible questions, I can send you some, but you need to bear in mind that your examiners may ask completely different questions. As for speaking in English, if I were you, I would practise as much as possible. Get friends to do mock vivas, and if you run out of friends just talk to yourself. English is my first language but I lack confidence talking about my work so that's what I will be doing before my viva.