contactor switched by remote contacts

It is not a question of it fusing, it is a question of voltage drop when you only have 48V to start with...you can lose a LOT of volts.

Ah, you got it.

No chance. longest 48V cable pair is 1 metre.

Panels deliver around 150V via 6mm2 cables from roof to charger and all else is standard 240V.

I plan to switch close to the consumer unit and keep the run upstairs to the vented tank and immersion as is.

We had a solar PV system installed back in the summer. They also installed a clever little thing called an eddi

The idea is to feed as little power as possible back up to the grid - as it's better financially to use it locally, if possible..

Yes this sort of thing was mentioned earlier, I am aware of them but they are expensive in comparison to using the battery charger to switch the supply.

In this instance there is no ability to export excess to the grid so once the battery is charged the panels just go open circuit.