Rub desired seasoning evenly onto all sides of fish.
Place the seasoned fish filets in a well-greased wire grill basket.
Grill in the wire basket on an uncovered grill directly over medium coals for 4 to 6 minutes for each 1/2 inch thickness fish or just until fish begins to flake easily when tested with a fork.
Meanwhile, for spread, in a small mixing bowl stir together mayonnaise, mustard and honey to taste.
To serve, spread the dressing mixture onto the cut side of focaccia slices with lettuce, fish, additional dressing mixture, and if desired roasted red pepper or fresh tomato, and top slices or halves of bread, split and lettuce leaves.
Optional roasted sweet red pepper strips or fresh tomato slices.