Before you start, preheat oven to 220°C (or 200°C fan bake). Bring a medium pot of hot salted water to the boil.
Prep potatoes. Spread in a single layer on 1-2 lined oven trays and toss with oil. Season with salt and pepper and roast for 25-30 minutes, until tender and golden. Turn once during cooking.
Add peas to pot of boiling water and cook for 3 minutes, until tender. Rinse with cold water to cool then drain well. Meanwhile, prep lettuce, radish and mint. Set aside in a large bowl.
Pat fish dry and remove any remaining scales or bones. Cut larger fillets in half. In a large bowl, whisk together batter mix and ice cold water.
Heat oil in a large fry-pan over medium-high heat. Once hot, coat each piece of fish in batter then cook (in batches, if needed) for 2-3 minutes each side, until golden brown and crispy. Add more oil between batches, if needed. Rest on a paper towel and season with salt and pepper.
To finish, dress salad with oil and vinegar and season to taste with salt and pepper. Prep lemon.
Serve fish and chips with salad, tartare sauce, tomato sauce and lemon wedges on the side for squeezing.