Cook noodles as per instructions.
Squeeze the lime through the watercress before filling.
Lay all the ingredients out in separate bowls on a workbench. Fill a large bowl with hot water and dip the rice paper into it until it softens - ensure the paper is completely wet - (but not so soft it's unmanageable) and lay flat on a large working surface.
Start by laying a small amount of noodles 1/3 of the way across the roll, leaving the sides free to fold them up into a parcel. Lay some watercress, carrot, shallots, herbs and a small sprinkling of chopped peanuts over the noodles. (Don't overfill them).
Lift the front of the rice paper over the filling and tuck it under the filling. Lift up the sides and tuck them in before rolling the rest of the paper around the spring roll.
Combine the dipping sauce ingredients and serve with the fresh spring rolls.
Note: making spring rolls is great fun and always enjoyed by children. Ignore the mess and encourage them to participate in the kitchen. That way they're far more likely to participate in eating a healthy meal.