Some great websites I use are sheinside.com and dresslily.com. I actually have a coat from SheInside that I got for £9 and it was from ZARA and was originally £80! Bargain of the year. I was over the moon when I saw it. So d go and check them out. The only issue with my coat was dodgy stitching on the inside but no one sees that anyway.
I'm a size...3 and small...but I normally don't purchase my clothing online, I'd rather go in and try it on because sometimes the cut might be too big or too small. I did risk it once and purchase clothing from the Hollister website, it was a jacket and it fit great (it was around $30). I usually shop at the clearance and for sale section of stores and websites (when and if I go to them).