I'm 5'5 at the same waist size. It's a pain in the ass, the best places I've found for decent clothing sizes that fit properly are in high end shops. I have a (I think mens) wool jumper/top thing which I wear over my shirts and it fits me perfectly as a small. I couldn't believe it! But shops like Politix, Oxford and a variety of the mid-high end shops are the way to go.