Paul G and I had another look at the wigeon today. In the same spot, but liked to keep some distance between us, even disappearing around the point at one stage before drifting back and starting to feed on shoreline. Based on articles online and Seb Reebers 'Wildfowl' the feelings are it could be a first winter bird coming into first breeding plumage. Still a bit more reading to do. After reading a bit more this afternoon, adult bird seems more likely. The white patch, as Dave suggests, is very obvious.