It's finished! Took me the best part of 9 months to make it, but it's finished just in time for baby's arrival, and I'm really pleased with it!
I'm particularly pleased with the border which I sort of made up as I went along. It adds an extra 6.5cm all the way around, extending my rather small granny square blanket (52.5cm x 39.5cm) into a much more respectable 65.5cm x 52.5cm. It also didn't look finished until I had crocheted the frill. I experimented with three different sizes of scallop (to treble crochet height, double treble height, and triple treble height) and decided the middle size balanced well with the rest of the design.
And here's the finished product! Nice to have something handmade and new ready for baby no. 3 to snuggle up in.