Heat oil in a medium-deep frypan over medium-high heat. Cook the meatballs, turning, for 3-4 mins, until browned (the meatballs won't be cooked through). Remove from the pan and set aside. Cook the carrot in the same pan, stirring, for 2-3 mins, until almost tender. Add the courgette, and cook for 1-2 mins, then add the meatballs and sauce and cook, stirring, for 3-4 mins, until the sauce is slightly reduced, and the meatballs are cooked through.