Hi- here is your way around it. NHS BMI claculator says that 7st13lb is still within healthy BMI range of someone 5ft3, so you should be fine to change this target (in fact NHS BMI calculator would let you get down to 7.7lb but thatis a bit low IMH) Besides, you are still 0.5lb from target so you haven't actually reached it yet, so you should be ok to change to 8st. However, be sure you really want to 8st and just under is quite low. Depends on your build wether that would actually look good
*reminises for a bit* back in the day when I had no weight issues I weighed just under 8st and it was a good healthy looking weight for me as I have a small build (and I thoughtI was FAT! Maybe i did have weight issues..just the other way)
Anyway, one long rambly post later:
1) If you want to change target to 8st you should be able to
2) Have a good think if it's right for you : this site is quite interesting for determing healthy weight based on height and your build (it all depends on your wrist measurement)
Clark State Community College - Weight Charts
3) I used to live in Leeds/Wakefield too ( in particular that limbo land known as East Ardsley) lol