Yes, this is the first house we have had with a moss problem. It faces north north west and we have a row of full grown deciduous trees running along a footpath about 50 feet from the house.
I think it is the this mix of north facing, shade, and humidity that is the cause of our moss problem. We are also roofed with old clay tiles, not slate or modern concrete 'clay' tiles, and the clay substrate is more moss friendly than the alternatives.
It is only the one face of the roof with the problem and most of the older properties on the same alignment as us have the same problems. But the substance the roofer sprayed on the roof has worked. The liquid probably drained into the more porous clay tiles, a bit like a drizzle cake, so hasn't benn washed off or washed away.