I've found what must be the solar relay under the passenger carpet this evening along with some other beefy fuses. I'll test those all tomorrow.
Seems my bulkhead plenum around the cabin air intake is not draining though, it was totally full of water and I can just see wetness on the 2 electrical connector plugs inside the blower housing
I've drained it now and I'll have a proper go at the job tomorrow.
Any tips or tricks very gratefully received