Hi Alastair,
So, the Band-in-a-Box apps are already 64bit, and I'm wondering if maybe you have an older version installed. At one point there was an iPad-specific app, which was later replaced with a single app that's for both iPhone and iPad. The older one I believe had "iPad" written on the icon. Perhaps you could try downloading the current one? Then again, if your setup is working well for you right now...