Well, I've tried different google accounts, stopping auto updates, etc, but nothing works. We have a different make android tv, in a different room and that doesn't suffer from the issues, so it's something specific to the philips model which I can't pin down.
My TV would be 1 year old in 2 weeks time - as such, I've taken the approach of returning it as faulty right now to avoid more complicated warranty/repair complications.
I can't keep continuously resetting it to buy a short period of time without an issue, or forever pulling the power cable out of the back as mikeinatruck mentions which does give a short term resolution until the smart TV software is launched, or the TV is turned off again.
Therefore it will be collected next working day, and I'll be buying a different brand. Shame, as I really liked the ambilight, but the issue has left a very sour taste in my mouth - especially coming at the time of the whole covid19 lockdown and the amount of pain it's caused me with the family complaining, so philips have been put on my list of "never again for a TV".
@mikeinatruck, I hope you have more luck than me