Thanks for info'; Proven gave me the same story. I'm now on their list for a replacement controller, which as you say should be free under the warranty. They also mentioned the 3kW diverter - I'll hold fire on that, and see how the new controller works...
I have also spoken to "Sustainergy" - Bob Robarts, who connected our turbine, and he says that one possibility is to remove one of the blades springs. Mine has 4 springs per blade. This would make it "cone" sooner in strong winds.

Regards Peter Benning

PS NPower, have just increased my 'generated' power to 11.41p / kWh exported - which they assume is 50% of my generated power.
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Peter61