I so want this centring issue to be sorted out, because I love this pattern (thank you for posting @charlotte ), and I would really like to have a go at it, but, I couldn't live with the off-centre issue.
Jessie
So my fix is:
Sew the zip to the right front as per the instructions for the view option without the placket.
Measure 2.5cm from centre front/centre of the zip (the placket is 5cm wide) and mark a vertical line on the right front, parallel to centre front.
Stitch the placket along this line right sides together, stitch seam allowance to jacket front and trim seam allowance close to this stitching line. Press the placket towards the centre front and topstitch, enclosing raw edge.
I'm sure this is not the traditional way to apply a placket but this is the same application used for the pocket flaps, and seems like the easiest fix. The only issue is that the placket may need to be a tiny bit longer, because it will start a bit higher up the neck curve, but I will just not stitch the placket until I have marked the line on the jacket front.
Also, if you are looking at the pattern, the digital pattern comes with 'copy shop' PDFs which I used for the first time. Two of the sheets were a bit bigger than A0 but I used Netprinter and chose the 'oversized' option. Their website was very easy to use and my printing arrived in two days.