I got brave. I did it. It worked!
Pattern (Burda kids 9551), dress fabric and notions purchased from my local fabric shop - Masons.
I'm really pleased with how this turned out. I've been having a lot of trouble buying clothes for Poppet because she has a long body and a small waist so I knew I'd have to make some adjustments to the pattern. I managed to make the perfect size by cutting the pattern to age 3 width, age 4 length in the bodice and age 5 length in the skirt. I fully expected to need to shorten the skirt as Poppet's legs aren't long, but nope, this was fine!
Given how awful the weather is at the moment I'm glad it can be worn with leggings.
The bodice and straps are interfaced and fully faced giving it a nice professional feel. I hand-stitched the hem to keep it light and tidy. The zip fitting isn't great as I don't have a lot of practice under my belt but it looks OK from a distance, and it works!
I'm definitely going to make another one, if only to practice the zip and piping. Poppet loves it.