At this point in time smart meters are only measuring power purchased from the grid. In theory they have the ability to measure export from a property, the exact methodology is not agreed. Export payments for existing FITs systems up to 30kw are deemed and there are no current proposals to alter this although there is provision in the primary FITs Legisalation to do so.
I don't understand what is meant by over-charging. We do not have and never have had net metering of PV systems in the UK. Domestic battery systems are installed 'behind the meter' and therefore are unaffected by and do not affect grid supply metering arrangements. Even where batteries are used in aggregation systems for virtual power plants and may discharge to the grid (not at all common) this would be transparent to the smart meter unless it was specifically being used as part of this arrangement which as far as I am aware has never been the case.
