Preheat oven to 350 F (180 C). Butter a 9x13 in (23x33cm) baking dish.
Prepare the filling: In a large bowl mix together the 1/2 Cup sugar, 1/4 Cup flour, tablespoon of cinnamon, and half teaspoon of salt. Gradually add the 1 Cup light cream and the lemon juice, stirring until combined. Toss the apples with this mixture, and then spoon into the prepared pan.
Prepare the topping: Mix together the 1 1/2 Cup flour, 1 Cup brown sugar, 2 teaspoons cinnamon, and 1/4 tsp salt. Cut in the butter with a pastry cutter until the mixture is crumbly. Sprinkle over the apples and pat down lightly.
Bake 45 minutes.
Prepare the toffee sauce: Combine the remaining 1 Cup brown sugar, 1/2 Cup butter and 1/2 Cup light cream in a sauce pan. Stir over low heat until the sugar is completely dissolved. Simmer until the sauce thickens.