Fish pie

Very good fish pie recipe which is not too heavy and creamy like some. Full of vegetables and easy to make. The leftovers also tastes good cold, which is a good thing as I brought the remains to work for lunch and didn't want to make my office smell of fish by reheating in the microwave. My only small complaint is that celery is a bit awkward to grate (or maybe it's just me?) so I would recommend using a food processor to grate the vegetables and cheese.