Just to close this off, new unit installed today and we now have IR back up and running. Even more remarkably despite having to reconfigure my TV activity from scratch in the Harmony app, both Alexa and HASS appear to have managed to remain functional.
Logitech were always the bees knees for Universal remote products but at some point they will turn the servers off 😞
No apology needed for the Hijack. I'm off to look!
C