Hey cate, I've just finished the foundation year at cardiff (haven't got my results back yet but hopefully I've passed!)
You're in the same situation that I was in; I have A levels in law, psychology and sociology and I was originally in cardiff uni doing law and criminology, but then decided I hated it, dropped out, and when I was looking through other courses to see what I would enjoy, i found out about the foundation year.
I wanted to do optometry when I first applied through ucas but once I saw that you needed science a levels (as I expected) I didn't look into it any further because I had no idea about the foundation year!
So I got my law tutor to ring the optometry school, and they agreed to interview me.. and I got in! So i reaaaally recommend the foundation year if you're really sure you want to do optometry. Just show them how much you want to do it, plus your work experience will help (I still don't have any!)
Hope this helps and feel free to message me if you have any more questions