Combine the oil, allspice, ginger, thyme, lime juice and chilli flakes in a small jug. Season. Place the steaks in a glass or ceramic dish. Pour over the marinade and set aside for 10 mins to marinate.
Meanwhile, heat a barbecue grill or chargrill on medium-high. Cook the corn for 10 mins, turning frequently until charred all over. Remove from heat. Cool for 5 mins. Using a sharp knife, remove kernels and place in a large bowl. Add the spring onions, beans, sliced chilli, coriander and lettuce. Toss to combine.
Cook the steaks on barbecue for 2-3 mins each side or until cooked to your liking. Transfer to a plate and set aside for 5 mins to rest. Thinly slice.
To make the lime aioli, combine mayonnaise, garlic, extra lime juice and 3 tsp water in a small bowl. Season.
Divide salad among plates. Top with steak and drizzle with lime aioli.