Top tuna with cheese, packing it on generously, and slide sandwiches under broiler. Broil until cheese melts and bubbles, 4-5 minutes. Remove tuna melts from broiler and serve immediately.
Mix together the tuna, mayonnaise and sweetcorn in a small bowl. Spoon the filing into the two rolls, wraps or pitta breads and serve. For extra fillings you could add lettuce, grated carrot ...