Only advice I could give is start with a hair appointment at a nice salon with an experienced hairdresser. The type of salon that have shampoos and treatments for sale as that may be just what you need.
If that doesn't work take susieblue's advice.
My hair's quite thin but the shampoos/treatments I get from my hairdressers plus using straighteners everyone thinks it's thicker.
gyp
Haven't been to the New Forest for years, are the horses still there?