If you can look at your diet and - subject to a number of caveats - add up its calorie content to around 2-5k a day, then your body is probably happy.
Technically speaking, I'm overweight for my height but that's what happens when going to the gym.
I suspect at least half the lifters on this forum are technically overweight, but I don't think any of them are worried.
If you're concerned enough about it, you'll restructure your lifestyle to do some more of the following:
- sleep;
- eat;
- exercise.
Personally, however, I wouldn't worry about 1 stone underweight... I'd be more concerned about what the content of your diet actually is...
EDIT: Just seen your follow-up post... you had pie, chips and bread in one sitting? Would you like some extra carbs with that?

In all seriousness, aside from being curiously unbalanced (in isolation - I have no idea what the rest of your diet is like), the spread of food like that posted above is almost irrelevant: was it a full dinner plate of food piled high? Or was it a Pukka Pie with a chipshop special?