I have got the same problem.. there are three settings "O", Auto and "I".. when I just want the water, the burner doesnt coome on.. however, if I turn it to Auto or "I", it works fine, but the problem is that the heating is on when I dont want it. So Im in the same situation as yours..
If you get an answer.. please share it with us as Worcester charge £185 for the call out charge..
Scotcruz
March 2007