Thank you to all of you who left sympathetic comments about my collar stand.
The interesting thing about this focus on white shirts only is that I am thinking a little deeper about the details rather than going on to the next thing like I usually do.
I have decided to do a collar band only shirt next and to try out Gigi's method . It seems to me that her system focuses on my area of difficulty and it would be interesting to see if that helps.
I am also considering the issue of interfacing, I used a sew-in woven, narrower seam allowances (I trimmed them down but obviously working with a narrower seam allowance to start with might make things easier to manipulate) and how much I need to topstitch.
I have had a good look at the wide presser foot on my Pfaff 7570 and the wide opening in it that is used to accommodate the 9 mm. zig zag. Of course the kind of control I need around that tiny curve at the front of the band is hard to achieve with this much open space in the throat plate, I suspect a straight stitch plate and a straight stitch foot, both of which would increase the proportion of metal holding down the fabric, would help. I should probably get one each of those. In the meantime I might try my grandmother's Featherweight which has a lovely straight stitch.
We're not resting until we get this collar issue dealt with, or at least I'm not.