Rigatoni with fennel sausage sauce

2½ tbsp olive oil 6 cut into 1.5cm-thick slices Italian fennel sausages 1 large peeled and chopped onion 1 trimmed and roughly chopped; reserve any fronds to garnish fennel bulb ½ tsp smoky paprika 1 clove, peeled and sliced garlic 2 tsp lightly toasted and then gently crushed fennel seeds 100ml red wine 400g tinned chopped tomatoes ½ tsp caster sugar 50g cut in half lengthways pitted black olives 500g rigatoni 30g roughly crumbled into 0.5cm pieces pecorino 1 rinsed and patted dry anchovy fillet 1 clove, peeled and crushed garlic 60ml olive oil 50g torn basil leaves