Put 3/4 cup of milk, sherry, Worcestershire, salt and pepper into skillet, mix and heat to simmer. Add fish fillets, cover and poach until done. With a slotted spatula, carefully remove fish to a serving platter and cover to keep warm.
Combine 1/4 cup milk and flour in a separate container. Add to simmering liquid in pan and stir well with a wire whisk. Add grated cheese and stir until melted and thick. Pour over fillets, sprinkle with paprika and serve.