Heat 1 tablespoon oil in a wok or large frying pan. Add the pork, prawns, crabmeat, garlic, ginger and spring onions and stir-fry for 5 minutes until just cooked through. Stir in the soy sauce and sugar and heat until bubbling, then stir in the coriander and set aside to cool a little. Meanwhile, prepare the noodles according to the pack instructions, then drain and add to the seafood mixture.
Mix the cornflour with the measurement water. Place a tablespoon of the mixture on one spring roll wrapper. Brush the side with a little of the cornflour mixture, then fold over and roll up. Repeat with the remaining seafood mixture and wrappers.
Fill a large saucepan one-third full of oil and heat until a cube of bread browns in 15 seconds. Deep-fry the rolls in batches for 3 minutes until golden and crisp. Drain on kitchen paper. Serve with chilli sauce for dipping and a herb salad, if liked.