After reading the reviews, I decided to get a 1 size bigger than what I wear. I wear size UK6 and bought a size 8 petite. For reference, I'm 158cm, 50kg, bust 80cm, waist 65cm, hips 89cm.
The jumpsuit is gorgeous! I loved the colour and the fabric. You can see that it is made with good quality material. However, I didn't like the fit. I felt like it was still not made for a petite around the neck(?) I never had this problem before with any jacket or shirt, but the collar was so tall, and it looked like I had a hanger hanging me from the back. It didn't look nice.
Also, it was restraining my movement around my bust and arms, and I dont even have big bust! While it was loose around my waist. For me probably it would have to be something like size 10-12 around bust and arms, and 6 for waist.
It might be ok for you if you dont mind feeling tight when you try to raise your arms to, for example, tie your hair, or wave at a friend, or pick something up from a high shelf, but for me, I felt trapped. I had to return it. It's very evry sad becasue I really liked the material and design.
