Final Update:
Two inspectors have just visited. They confirmed that this inspection is related to the local foulbrood outbreak, obviously. They were both very friendly and professional, of course.
Beatrix had the all-clear, then I had a really scary moment halfway through Charlie's colony when they both went a bit quiet and poked a rather sickly-looking larva out with a stick. They were in the process of doing a foulbrood test on it when the heavens opened. We all belted for cover to wait for the downpour to pass by (having closed the hive up again, of course) and waited for the test result.
It was a bit like waiting for a pregnancy test stick again, but this time hoping for a negative! It did eventually come back as a negative result, a massive relief of course.
Dipsy's colony were as moody as ever, so we saved them till last, and we've finally found out why we've been noticing that this one smells different - it's the ivy honey, really rather stinky!
It was a great experience and I'd thoroughly recommend it. It did feel a bit strange to see somebody else inspect my bees (it reminded me of the dentist inspecting our children's teeth for the first time!) but it was a great opportunity to watch professionals at work.