Hello Groucho,
My experience of copper coat in the Orwell (which is well above average for fouling) is that it is not as efficient as annual antifouling.
Short of hauling the boat out every 8 weeks, I am using a scrubber on a pole system to keep fouling under control.
The boat is now in Woolverstone marina so I am able to berth with both rudder and keel up, which helps. With this method I’m hauling out once a year for a scrub, folding prop service, copper coat abrasion, keel check and topside polish.
I haven’t looked at alternatives to copper coat yet as what I am doing seems to be working. Doubtless as the it gets closer to the ten year copper coat lifetime I will investigate.