When you say ...
... I got into the car and switched the infotainment unit on to disable DST on the clock. Then I switched the infotainment unit off.
... do you mean you simply used the on/off button without starting the engine ? I don't think doing that actually starts the infotainment unit, it just turns the audio on/off;
Nope. I just pressed on/off because I didn't have my keys with me (the car is kept unlocked in my garage). Just been out and checked and pressing the green on/off button causes the Honda logo to appear followed by the usual stupid warning message and Ok button. Looks and acts exactly like it does normally. I was able to temporarily change the audio source from iPod to Bluetooth and it streamed from my coat hanging up in the lounge.
You know, that if that's screwed it up again I'm going to mutter something about you under my breath tomorrow morning, don't you?
And the clock is correct - I glanced it a lot on my drive back home tonight due to heavier than expected traffic around Banbury.