Place the apples and pears in a medium, heavy-based saucepan with the orange rind and juice, honey and ginger. Bring to a gentle simmer, stirring occasionally, then cover and simmer for 10 minutes until soft and slightly pulpy. Add the strawberries and cook for a further 2–3 minutes until soft, yet still retaining their shape. Remove the pan from the heat and transfer the mixture to an ovenproof gratin dish. Set aside while making the crumble.
Put the flour in a bowl and stir in the flaxseed. Add the butter and rub into the mixture until it resembles chunky breadcrumbs. Add the oats and again rub the fat into the mixture using your fingertips to distribute well. Stir in the seeds and sugar then sprinkle over the fruit.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 30–35 minutes until the topping is golden. Serve the crumble warm.