Preheat the oven to 180 C, 160 Fan Gas 4 and preheat the grill to medium. Slice the tomatoes and arrange overlapping on individual plates . Sprinkle with a little salt and pepper.
Put the fish into a buttered flameproof dish. Divide the rarebit mix into four pieces and pat out on your hands to about 2-3mm thick. Lay it on top of the haddock.
Colour under the grill until golden then finish in the preheated oven for 3-4 minutes.
Add the chives to the Vinaigrette and spoon over the tomatoes. When the haddock is cooked place on top of the tomatoes and serve,