I did this a couple of days ago for a vegan friend who came to stay and it is really good.
Used Discovery apples from the shop but friend brought his own 'cooking' blackberries.

I Sliced the apples into some lemon juice, mixed them with the blackberries and poured in some Terrasana Maple syrup.

For the crumble I used organic oats, fine oatmeal and ground almonds in equal quantities, forked in some light olive oil and some more Maple Syrup so it was 'crumby'. Piled it on top of the fruit and cooked gas 6/ 180°C for 30 mins.