Disable gas boiler when not needed

[cmcgerty]

Hi, I'm new here so send me to the faq or suggest a search term if this is a totally dumb question.

If I use spare solar PV energy to heat the hot water tank via the immersion heater with an iBoost immersion controller or similar, how do I ensure the boiler won't also run it's normal schedule? Does it have the ability to know that the water in the tank is already hot?
Even though we have a Nest thermostat, I don't think there is any temperature detection at the tank, or if there is, how I would control it.

System:
Bosch Worcester Greenster system boiler with twin emersion pressurised tank.
Nest gen.2 learning thermostat.
14 x 285w solar PV.
SolarEdge HD-Wave inverter.
Pylon 2.4kwh US2000 battery.
Sofar ME3000SP battery inverter.