Cous cous alla Trapanese

My sister, recently holed up in Trapani with ferries to the Egadi islands suspended due to adverse weather conditions, discovered a delight of the western (more arab influenced) part of Sicily. Cous cous alla Trapanese, is surely one of the best dishes around, unfortunately not present in this 'Greek' side of the island.
Here is a receipe I have translated:

For 6 people
1 kg. Mixed fish, shell fish and seafish, i.e seabass, clams mussels etc (according to availability)
500 gr. Mature Tomatos
2 cloves garlic
2 stalks of celery
2 carrots
1onion
1 handful of parsley & 1 bay leaf
1 pkt of saffron1 pinch of paprika
salt and pepper to taste
chilli pepper to taste
500 gr. cous cous

Clean the fish, crusteans and seafood. Put into a pot the fish heads and tails and any unused parts of the seafood, cover with water and add the bayleaf, some of the parsley, carrot and celery with half the onion, salt and pepper. Cook for 40mins and strain, keeping the broth separate. In a separate pan, the rest of the veg and condiments and herbs- its better to keep the garlic whole. Then add the fish, after shellfish Put HALF broth in with the ingredients. Add the tomatos, and leave to cook for 15 mins. Add any seafood, and any more salt needed, and continue to cook for 10mins.

At this point, you can get out your ‘couscoussiere’ if you’ve recently been on holiday to Morroco. If you haven’t, cook the cous cous in the normal way, adding olive oil and the rest of the broth (they expect you have the said couscoussiere,I can't guarantee what cous cous is like with fish broth added instead of water with normal cooking).
Its now ready.