Apple coffee cake with rolled oats crumble topping

I wanted to make an apple coffee cake so I found this recipe and used it as a guide. I am currently in Ireland and they have self-raising flour here which already has baking soda in it (I think). So I didn't add any soda to it. At the last minute I did add a tsp of baking powder, which I am glad I did because I forgot to add the eggs.

Here is the recipe as I made it. It was quite crumbly and not very high because of the lack of eggs, but it is very good, although too sweet. The original recipe had even more sugar than I used.

Mix in large bowl
1/3 cup melted butter
1 cup packed light brown sugar (I think 1/2 a cup would be enough)
2 large eggs (I forgot these)
1 cup sour cream (I used milk because I didn't have any sour cream)
1 teaspoon pure vanilla extract (I didn't use this either because I didn't have any)

Mix in medium bowl
2 cups all purpose flour (I used self raising)
1 teaspoon baking soda (I didn't use because self raising flour has it)
1 teaspoon ground cinnamon
1 tsp baking powder
1/2 teaspoon salt
2 cups peeled, cored and chopped apples (I used one chopped unpeeled granny smith apple and 1/2 cup raisins)

Crumble Topping
1/2 cup packed light brown sugar
1/2 cup rolled oats (called for flour)
1/2 teaspoon ground cinnamon
2 tablespoons melted butter (called for 4 tbsp)

Add dry ingredients to wet and fold in. Sprinkle crumble topping on top of batter.

I baked it at about 350 in a convection oven and it took about 25 minutes. If it had been a regular oven it would probably have taken more than that. The original recipe called for 35 to 40 minutes.