I'll install the Solis in the loft on the gable wall alongside the hybrid.
The current 3.68kW hybrid and the Eddi are fed from a mini CU that the installer put on the wall next to the meter. That in turn is fed from henley blocks.
It has a few spare ways and I think I'll just run a 2.5mm cable down from the loft to a bidirectional 10A RCBO.
This is probably short term as I plan to put six more panels on the flat roof, subject of course to approval from The Boss, when we re-roof it later this year. I'm not keen to run DC cables on the flat roof, and they'd need some shade mitigation, so I think I'll go for Hoymiles microinverters for those.
I've also measured up that gable wall and found four panels will fit there. That's a harder sell, though.