Thanks @Jodi_S,
Just to be clear, Sebastian only offered one option (not a solution) and that was to have someone come and replace everything that I currently have. There's no clarity on why I've had the problems that have occurred over the last 2+months, nor any assurance that replacing all the wiring and the Hub would have any effect on that at all, just the single offered option of having someone come and do what the other 6 engineers have already done.
Honestly, if there was any indication that anyone knew what had caused the problem, or that there was any confidence that ripping it all out and starting again would make a difference, then I would onboard.
But there's not.
In his defence, Sebastian was very polite. It's just a shame he wasn't trying to contact me a month ago after Engineer #6 had tried and failed to resolve this, rather than today, after I've sent a note saying i'm done.