Both Leisa and Kat have offered to replace my bag if necessary, so I'm sure it will all work out fine.
The bag itself is fine, fits really well; it's just the bit at the top, the decorative strip with the cord running through, that is a bit on the narrow side.
I'll (carefully!) work with it for a couple of days, to see if I can get used to it; if mine really is slightly snugger (ha, that's a very different word in Dutch!) than the rest, a replacement bag would help of course, but if they're all like this then it wouldn't do much good.
Edit:
Exactly, I might just have to give myself time to scale the bag-learning-curve!