I don't own a turbine like yours but I would suggest that you contact your local Trading Standards officer at your local Council, and a solicitor or the Citizen's Advice Bureau. You have rights under the Sale of Goods Act. If your Turbine has been that bad you should be able to have it removed and get a full refund. It is not a cheap toaster or a throw away pen, it cost you £19,000 so should work. Don't be afraid to make a fuss, you were sold a Wind Turbine, not a garden ornament.
Also, contact the Energy Saving Trust who gave you the Grant. They are very interested in problems with Turbines and Installers as they give accreditation to both. They can get things moving as they hold the purse strings.
I am lucky. I had teething troubles with my Proven, but my installer went to great lengths to find a solution and ensure I was a satisfied customer. Still does.