Just looking through flexiorb further:
Electrical Energy Storage Systems (EESS) If you have a renewable energy system in your home, such as Solar PV, any excess electricity you produce (and don’t use) is returned to the National Grid. UK households tend to consume more electricity in the morning and evening, therefore you can lose a...
www.flexi-orb.com
Third paragraph from bottom states:
DNOs are rarely informed of EESS being connected to the grid – which could put a strain on the network. Registration would help DNOs manage the network. Flexi-Orb will track all this and automatically complete the G98 or G99 DNO notification.
It would suggest if your install is registered through that they do the G99 for you. On the flexiorb certificate I have it does state the system intalled power of 4.5kw (5kw inverter 4.5kw of panels) and provides the serial number etc of our electricity meter. So I am guessing going by that it is all actually legit.
Another thing I have now seen is with the flexiorb registration we were also given a CPA insurance certificate.
Possibly worrying over nothing then.
The problem is these days I have NIL trust for any tradesmen of this type, unfortunately, and the salesman for our installer is a bit of a wideboy and claims to know little about how it actually all works in the background but is adament they are all "legit" and that it is his brother that sorts all of that stuff out - and its exactly that attitude that never fills you with confidence. To be fair to the guy he could sell sand to the Arabs though.