Heat grill to high. Empty beans into a pan, stir in tomatoes and cook over a medium heat for 5 mins. Divide the bean mix between tortillas, sprinkle over a small handful cheese, then roll up the wraps. Put onto a baking sheet, scatter over another handful of cheese, then grill for 2-3 mins until the cheese is golden and bubbling. Serve with the guacamole on the side.