I was surfing the net and I came across to English in guía blog where I've found this fantastic document. In the embedded one you can find some useful expressions you can use during your exam. Now, you only have to read as much as possible, listen to English and practise it in our weekly Friday lessons.
Besides, in this powepoint you will be able to practise the functional language you need for your speaking test. The structures are very helpful, so REMEMBER them!
Finally, I found out another great article, published by Saro Rosales. A list of possible topics and useful expressions are included. So, don't miss it! ;)