I’d put money on that been b🤨llocks from Ohme rather than National Grid. Yes NG is actively reviewing its footprint just as other companies are, but they aren’t going to say e.g we can’t supply for a heatpump, just because you have an EV charger installed or may want a second EV charger, as they save the planet or so they say, so its a bit of a hypocrytical statement. You can view how NG’s is reviewing its footprint in the link.
https://www.nationalgrid.com/responsibility/our-environment/our-climate-transition-plan
However, it does depend on your homes maximum load and whether the substation has enough spare capacity to upgrade. Also, as discussed previous, Ohme chargers can’t be daisychained so say one car is on charge, it will charge at 7.4kW and the load is shared if 2 vehicles are being charged at the same time. With Ohme chargers, they would have to reduce the kWh supplied on both chargers permanently and this is probably what Ohme is getting at, but doing a Labour and blaming someone else. Like wise they aren’t capable of doing solar and imo are crap!