When attaching the waistband it is significantly smaller than the waist opening, so don't stress about making it fit and pinning! Just line up the back seams and secure, then place the waistband down on your machine (sewing or overlocker). Start sewing as usual, except gently pull the waistband toward you so that it stretches as you are sewing (the seam may get a little wavy, but don't worry because that will dissappear with pressing and washing). The result is a perfectly fitted waistband!
If you are using cotton jersey like I did, consider not making a hem on the pants..I left mine as they were and they are begining to roll like an old t-shirt, it actually gives a nice finish!
These pants don't have to be casual! You can make some very nice dress pants in a couple hours using a rayon, silk, or wool knit.
I think with a little modification these could be great maternity pants. Use fabric with a little Lycra/spandex (either just the waistband or the whole garment) and make the waistband wider to cover the baby bump. I don't have any children at the moment so I don't have any experience with maternity clothing, but I will definetly try this out when the time comes!
After I get my affairs in order I promise to post about my adventures in London! Stay tuned!