Anyway, I made few changes to the original recipe by reducing amount of sugar and lemon juice used for the filling ( this is about nothing but my own preference!) and while the original recipe doen't call for any alcohol, I abruptly decided to add some rum when I spotted it while I was making the filling!
Here is my version ( adapted from here)
For the Crumble:
1.5 cups rolled oats
3/4 cup light soft brown sugar
1.5 cups plain flour
1 tsp bicarbonate of soda
0.5 tsp salt
3/4 cup butter, melted
1/2 cup soft light brown sugar
2 TBS cornflour (cornstarch)
3/4 cup water
1 cup sultana raisins
the juice and finely grated zest of half lemon
1 tbsp dark rum
Preheat the oven to 180*C/350*F/ gas mark 4. Lightly butter an 8 inch square baking pan. Line with baking parchment, leaving an overhang to help lift the baked squares out.
Place all the ingredients for the filling in a saucepan, with the exception of the rum, lemon juice and lemon zest. Cook and stir until the mixture boils and thickens. Remove from the heat and stir in the rum, lemon zest and juice. Set aside.
Whisk the oats, brown sugar, flour, soda and salt together in a bowl Pour the melted butter over top and mix well together until nice and crumbly. Press half of the crumbs into the prepared pan. Spoon the sultana filling evenly over top. Sprinkle the remainder of the crumbs over top and press down lightly. Bake for 25 - 30 minutes until golden brown and firm to the touch. Allow to cool completely before cutting into bars to serve.