Cook the noodles following the packet instructions. Toss with the sesame oil and set aside to cool.
Brush the steaks with the olive oil. Heat a griddle pan over a high heat and cook the steaks for 1-2 minutes on each side for rare meat, or 2-3 minutes each side for medium-rare meat, depending on thickness. Season well and leave to rest; thinly slice.
Meanwhile, for the dressing, put the sesame oil, lime juice, sugar, fish and soy sauces into a small, lidded jar to transport to your picnic.
Put the carrots, radishes, cucumber and noodles in a lidded container and toss to combine. Add the lettuce, spring onions, beef, sesame seeds, herbs and chilli; seal the container. Dress the salad just before serving.