Moss is a symptom of a problem and isn't really a problem of its own. It only happens when something isn't allowing grass to thrive. Heavy shade, compaction and/or soil problems are the biggest offenders -- often in combination. Killing moss just delays the day where the problem(s) have to be faced and solved.

Some mosses turn black when they dry out and will green up when moisture returns. Perhaps your mosses have been replaced by a new species? Other than that, all I can think of is that something has resulted in conditions being unsuitable for them. Changes in light, or maybe the water from the tap has left calcium deposits that changed the pH of the substrate? I'm just speculating of course.

Moss might go away by itself once the lawn is getting proper care. How often and for how long do you water? With your current temps you should be deep watering (3 cm) once a month. Mowing height should be the highest setting on your mower (10 cm). Fertilizer should be 3x per year (Spring Bank Holiday, Summer Bank Holiday, and Guy Fawkes Day). If you are going to reseed the thin spots, you'll need a fine fescue type grass that is good for shady areas. Some of the areas look too dense even for shade tolerant grass, but you might give it a try.

Thanks, jane and Al. Oddly, this is one of my least watered orchids (realizing that doesn't mean it's not overwatered) -- pretty much 'pour-through' maybe once every couple of weeks, lightly misted every 2-3 days, but very thoroughly soaked prior to out-of-town vacations 4x annually. It sits in a mixed bark/sphagnum/perlite medium, and the plastic container has air holes poked in the sides and bottom -- lots of air flow and drainage, I think. I do think this is a good time to carefully pull the fern out before it overtakes. Perhaps a very low bar to set, but I'm a novice: if the leaves and roots look fairly healthy, and the plant flowers, I feel I'm doing something right. :) It's recommended to freshen up the sphagnum moss about every year anyway -- something I'll really need to work on.