Congrats on the weight loss. You have taken the first step at the club. JUST ASK HER OUT!!! Then tell her how you've felt since you were 15/16 and that you were overweight and was too embarrassed to ask her out then but now you gotten your self confidence and now you want to tell her the truth about how you've always felt about her. Be yourself and most importantly BE HONEST about your feelings for her.
Okay, I'm female albeit past the dating game. I'd call her and tell her I didn't hear her answer but didn't get a chance to ask again. Then ask her if she wants to go out. At the worst she says no. At the best she doesn't sit around thinking, did I send out the wrong signals? I said yes and he didn't do anything, guess he didn't mean it.
I can't get past the I lost 6 stones part. Is that still used as a measurement in some places? Do scales actually say "stones" on them instead of pounds or ounces or whatever?
This is for future reference, but be a man about it. Do not ask hypothetical questions or dictate an anticipated reaction. Do not ask a girl you like out (as in a girl you already know who you wish to date) when you are drunk. You should also keep in mind that this isn't someone you really know anymore. Aside from that you really are over thinking this. The forum gets tons of posts like this, and they all sound the same.