Thanks STX - as I suspected - for the safety of people working on a fault, your local solar. system would have to be shut down. They could not risk back-feeds. I think the only way around it, would be a totally independent system from the mains, involving a battery bank, for night time power.
The batteries would be horrendously expensive - & life limited.

The only alternative way, would be with the auto start SBY Generator method, of two interlocking 3 phase contractors - they cannot both be powering the load at the same time. For Caroline, that might be the cheaper method, as the Genny would only be needed once in a blue moon - we hope.

I think there is an old Genny set at Orford, though if it was designed for powering the original TXs - it would be huge & overpowered - & drink the diesel ! There will be some nice 50kva ones at the old USAF base at Woodbridge -