Mix all the spices together in a small bowl and use 2 tsp to coat the chicken. Cover and allow to marinate for 10 minutes while you prepare the sauce.
Place a large saucepan over a medium heat, add the garlic, tomatoes, stock and 1 tbsp of the Mexican-style spice mix (you can save any remaining spice mix in a jar to use again). Bring to a boil, then reduce the heat and simmer for 15 minutes.
While the sauce simmers, spray a frying pan with low-calorie cooking spray and place over a medium heat. Add the chicken and cook for 2-3 minutes until sealed on all sides. Add the peppers and onions and cook for a further 5 minutes. Remove from the heat.
Whisk the cream cheese into the spicy tomato sauce until melted, and squeeze in the lime juice. The sauce should be the consistency of single cream. If it seems a little watery, increase the heat and simmer rapidly for a few minutes until thickened.
Remove 200ml of sauce and put aside for the topping. Preheat the oven to 180°C fan.
Stir the sauce into the chicken, peppers and onions, add the sweetcorn and coriander. Pour half the fajita mix into the bottom of the ovenproof dish. Lay 3 lasagne sheets on top and add the rest of the fajita mix and then the remaining lasagne sheets. Pour the reserved sauce over the top and sprinkle on the grated cheese.
Place on a baking tray and into the oven for 40-50 minutes until the cheese is golden and bubbling and the pasta feels tender when you insert a knife.
Allow to rest for 5 minutes before serving.