believe it or not, but nandos is one of the healthiest "eat out" options available. The chicken, of itself, has almost no carbs and no fat. You can get a quarter/half chicken and NOT eat the skin, or a chicken breast, but I usually opt for the tenderloins. They're very tasty, pack a massive 43g protein, only 1 g saturated fat and only 3g carbs. You can't get healthier than that!
The chips are a big no no, but you seem to know that. They are packed with saturated fats and carbs.
As for the salad, it's a good option. As long as you don't use the fancy dressing they provide you with, the salad is simply as fresh as it would be if you grabbed the ingredients from your backyard (maybe not that fresh, but there's nothing in the salad if you don't add dressing).
Don't know about the corn, it's the only vegetable I know of with NO nutritional value and that's packed with carbs too lol.
If you get the tenderloins (or another chicken, NO bread) with salad, you can easily stick to your diet. BTW, the sauce also makes a difference. Again, believe it or not, the extra hot sauce is lowest in calories and virtually no carbs and no fat. If you can handle the heat good for you.
I have a friend who owns and operates nandos, this is generally how nandos nutritional info goes, but I've also noticed quality and amount of food changes from nandos to nandos.