Preheat the oven to 200°C (fan 180°C)/400°F (fan 350°F)/gas mark 6 (fan gas mark 4).
This is a really simple one-pot recipe; just combine the onion, cherry tomatoes, cannellini beans, oregano, mustard, garlic, most of the bunch of thyme and the cider in the base of a small roasting tin. Lay the sausages on top of the vegetables, drizzle each with a little oil and cook for 20 minutes or until the sausages are just beginning to brown. Carefully remove the tray from the oven and turn each of the sausages over. Season the upturned side with salt and pepper then return the tin to the oven and cook for 20–25 minutes until the sausages are cooked through.
Serve sprinkled with the remaining thyme.