Stir in the tomatoes, wine, parsley, pepper, sugar and seasoning salt. (There are many seasoned salts: I like one we get, which has finely ground coriander, herbs and a touch of dried pepper flakes in it).
Bring to a boil, stir, and add the fish fillets - in batches if your saucepan is small. Simmer the fish no longer than 7 minutes - less if they are quite thin.
Transfer the fish carefully with a slotted spoon to a serving dish, and keep warm in an oven.
Boil the sauce until reduced by half and thickened. (Hard to guess how long it will take).
Then stir in the cream, and again let it reduce over fairly high heat.
Taste the sauce in case you want to add something extra, like grated nutmeg.
Pour over the fish.
Serve with rice or mashed potatoes, young peas (or a sweetish veggie like butternut or pumpkin) and a green salad.