Preheat the oven to 200°C/400°F. Line two baking trays with parchment or a non-stick silicone mat.
Place the potato batons onto one of the trays. Drizzle on half of the olive oil. Sprinkle on the paprika, salt and pepper. Mix everything together with your hands, then arrange on the tray in a single layer. Place in the oven, on the top shelf for 15 minutes.
Meanwhile, place the fish on the other baking tray, skin-side-down. Pat the flesh of the fish dry with a piece of kitchen roll.
Place the breadcrumbs in a bowl and drizzle over the remaining olive oil. Add a pinch of salt and pepper, then mix with a spoon, until the breadcrumbs are coated in the oil. Spoon the breadcrumb mixture on top off the fish fillets.
Once the chips have been in the oven for 15 minutes, turn over using a spatula and move the tray to the middle of the oven. Add the fish to the oven, on the top shelf. Cook for 10 minutes, until the chips are golden and the fish is cooked through.
Whilst the fish and chips are in the oven, steam or microwave the petit pois until cooked. Place in a bowl and mash with a fork. Stir in the lemon juice and crème fraiche. Top with the lemon zest.
Take the fish and chips out of the oven. Divide between two plates and serve with the lemon smashed peas and a dollop of tomato sauce if desired.