I know more than one person has asked about how the regular sizes compare to petites, so here are the measurements of the UK 6 / US 2 regular in black:
15" across the bust
12.5" across the waist
17.9" across the fullest part of the hips
~14.25" across the hem
15" from centre back to waist
35.75" total length (from shoulder to hem)
In other words, it's longer than the UK 4 petite but not drastically larger - 0.5" in the bust and 1" in the waist. As Petite Asian Girl has mentioned, hemming could be tricky because of the narrow hem and short back slit.
This dress will be a return for me because I found the skirt looked and felt awkward when moving around, but I'm not used to pencil skirts so your mileage may vary. Here's a photo anyway:
The bust fits snugly but there's a little room in the waist (I'm about 31-23-32 at 5'7"). The fit is decent, but the skirt shape just wasn't right for me.
ETA: just wanted to mention that the side zip does go all the way up to the armhole. I specify this because those side zips that don't quite reach the armhole (H&M designers seem to be fond of them) are a dealbreaker for me, haha.