Combine the barbecue sauce with the tablespoon oil, rub lightly over the fish fillets, and leave in a non-reactive dish at room temperature while you prepare the rest of the dish.
Mango sauce: Heat the oil in a pan and add the onion, cover and cook 5 minutes, then add the mango, orange juice, hot pepper and honey, and stir well. Simmer, uncovered, for about 7 minutes. Puree the mixture in a blender, season with salt, put in a bowl, cover, and keep in a warm oven.
Corn relish: Combine all the ingredients (corn kernels down to the oil). Season to taste. Put in a bowl, cover and put in warm oven with the mango sauce.
Also put 4 - 6 plates in sam oven to warm up.
In a pan (can use same one you used to make the mango sauce) heat some oil until hot. Fry the fish fillets for about 2 minutes per side, until JUST cooked through.
To serve: Spoon some mango sauce in the centre of each plate. Set a fish fillet on top, and spoon some corn relish over the fillet. Serve immediately.
Nice with simple boiled potatoes or baby potatoes, and a mixed green salad.