What can I add to my work lunchbox to make it more substantial? I currently put chicken pieces, couple slices of ham, few tomatoes, slices of cucumber and a bit of pepper.
I don't want anything too carby e.g. I used to put cous cous or sweetcorn in to bulk it up but I think they're too carby and obviously I don't want anything fattening. Any ideas?

Handful of nuts? Or sugar snap peas and baby corn?

A black pudding and two plums.

Bananas, pistachio nuts, cashew nuts, peanuts, strawberries, babybels, raisins

Lettuce, grated carrot, grated courgette, mayonnaise, hoummus

Do you have access to a microwave? If so, just take leftovers. I make enough food at the beginning of the week for several evening meals and lunches and pre-pack them all in individual-size tupperware bins in the fridge. Anything from various meats and veggies, casseroles, soups, pasta, rice, stir-frys, etc.

If you don't have access to a microwave and need cold or room-temperatures foods, the best way to open up your menu creativity is to eliminate the bread from your sandwiches. Use tortillas, pitas, bagels, pita chips, even lettuce cups, and so on to eat with the cold cuts or chicken salad. Or just pack snacky-type lunches of some combination of things like cheese, crackers, nuts, yogurt, fruit.

Ok I take carrots, red, orange and yellow pepper, celery, Mangtouts and usually dip them in phillidelphia light or hummus. Maybe some cooked chicken breast too.

I also take a box of mixed fruit like strawberries, raspberries and blueberries and a small pot of fat free greek yogurt.

Then my snacks usually consist of a piece of fruit, a fat free yogurt, babybell light, a small handful of mixed nuts, dried fruit is great I love craisins and raisins, dried apple, dried mango and dried papaya is amazing. I usually have about 2-3 snacks a day.
Also I only drink water or water with lemon juice.
Hope this helps

Radishes, they are nice and crunchy and more substantial than other salad items.

A small tin of baked beans

a yorkie bar