It might not look very exciting (ok, I admit it doesn't look appealing at all) but I love some bubble and squeak the day after a roast lunch and it tastes great. I often do extra portions at Sunday lunch to guarantee there's enough for an easy bubble and squeak the next day. It's also become a Boxing Day tradition in my family.
Part of the beauty of this dish is that you don't need exact measures, just use what you have. The leftover veg you have is pretty interchangeable with only the potatoes being vital to hold everything together.