Heat the grill. In a bowl, mix together the pork, garlic, lemongrass, fish sauce and half the coriander. Season with pepper. Mix well and form into 8 patties. Rub each one with the oil and a sprinkling of sugar, then place on a rack in a baking tray.
Grill the patties for 3 mins each side until golden brown. Meanwhile, in a large bowl, cook the rice noodles following pack instructions. Drain the warm noodles and serve with the patties, chopped spring onions, remaining coriander and a drizzle of sweet chilli dipping sauce.