lol you still haven't asked him out?? hmm... that's a problem i guess ummm... lets see what kind of creative ways my slow brain can conjure up...
1. you're too shy to ask
2. you've already said no once
3. you think you're attracted to him now
4. you don't know if he feels the same
hmm... you really like sticking us advisors in impossible situations don't you??
well, if i it was me, i'd probably go up to the person introduce myself, ask him if he remembers you since you're always at the supermarket shopping, and then ask if he might be up for lunch together during the week...
you will get two answers:
1) a yes: means that you've got yourself a new friend/bf
and that'd be a congratulations from me OR
2) a no: which is kinda self explanitory
however since you said that he's taken an interest in you before (asked for your number??), i'm sure that the chances of a yes will be good ^^