Wow, there are some great ideas here, some really creative! Its's good to think that it might just be a quick phase anyway. I will make sure I have some distractions to hand and was it until the weekend when my husband is home and the babies are in a good mood before messing around getting the fit right. Once I've got that then I guess it should be at least no worse than getting a disposable on.
If all else fails I might try and find one of those changing mats with harness, but it looks like nobody has stock at the moment.
Thanks again, and GilbertandMartha your hat sounds genius!