I'm 6'3" and i weigh around 13 stone. I used to weigh 17 stone, but i recently lost it all, purely by cutting junk out my diet. While my BMI is just under 22, which is apparently "normal" however, I still have a lot of fat stored in my belly, around my hips and lower chest, but, i want to get into 6 pack body fat area. What should i start doing? Continue running? Lift weights?

Sorry if this seems a bit vague, im not really an exercise expert :/

Short answer:

Adjust your calorie intake, lift wieghts to not burn off any muscle you have and do a little cardio to help with the diet.

http://forum.bodybuilding.com/forumdisplay.php?f=16
Go here, read stickies. If you are serious about getting fit, read these.

2 tips after reading some material are:
1) Do not starve yourself, slow and steady make things permanent
2) Do not do cardio to lose wieght, use it only to speed up the process your diet creates. People do hours of cardio and lose wieght, 2 months later they burn out and gain all the wieght back because the never fixed there diets.

If you have any more questions, feel free to pm me. I can help you out. BUT you need to read the stickies first!

Obviously you are well on your way, you lost 4 stones so just keep on keeping on. If you start to slow down just cut down your carbs more.