Ok, from taking a quick look at the Bondwell 12/14 boot process, it looks to me as though it actually ought to wait for the Recalibrate/Seek function to end before it goes and does Sense Interrupt Status.
So, I've added code to set the execution mode bit of the main status register during a seek or recalibrate function, and moved the nec765_idle() call from nec765_seek_setup() to nec765_seek_complete(), as nec765_idle() clears the execution mode bit.
If this makes sense to everyone, I'll go and commit it to SVN. I have no software for the Bondwell, so I can't test it any further than it complaining after wanting a system disk. The PCW driver still works with this change, and I also quickly tested the CPC and X68000 drivers, just in case, which also seem to still work.