Bring a large saucepan of salted water to the boil over high heat. Add green beans and butter beans. Cook for 3 minutes or until bright green and tender. Using a slotted spoon, transfer to a colander and refresh under cold water. Pat dry with paper towel. Return water to the boil.
Add potatoes to saucepan and cook for 12 minutes or until just tender. Drain and set aside to cool slightly. Cut in half lengthways.
Preheat grill on high heat. Place pancetta on a lined baking tray and grill for 5 minutes or until crisp. Drain on paper towel. Tear into small pieces.
Arrange beans, potatoes, pancetta and avocado on a platter. Combine mayonnaise, lemon rind and 1 1/2 tablespoons lemon juice in a bowl. Pour dressing over salad. Season with salt and pepper and sprinkle over dill.