So after much research, in 2020 I bought a used 2017 65kmiles T8 R-design, had read this thread [!!] so hunted down an insured ALA-RAC warranty that covers EV Hybrid/ERAD failure.
October 2023 @ 103k miles and my ERAD is still good, no problems with that and I do LOTS of EV only trips so it gets a good workout, is regularly charged multiple times a day.
What DID go wrong in Aug was the charger module, which sits on top of the ERAD, symptom was yellow charge light and no charge, car thinks it's plugged in when not. My ALA-RAC warranty covered this £1,600 repair bar £70 of fuses [3-year warranty had cost $500 and had 2 weeks left to run!] Volvo Swindon very helpful.
"What's this got to do with ERAD failure?" you say!
Weeeelllll I discovered this company in Hungary that appears to be a Volvo hybrid specialist. Turn on translate and check it out, repairs and refurb of ERAD and Charger unit I had the issue with!
https://vszerviz.hu/2021/12/t6-t8-toltomodul-obc/
To quote the above site..
"In the case of new Volvos, the car transmits very few error messages to the driver, so it usually does not indicate a failure of the transmission clutch (however, the source of the error is immediately visible during factory diagnostics).
There was a precedent that we repaired it, but in the vast majority of cases, the solution is to install a new structure.
In our service, we can repair a fault in as little as 1 day."