There may or may not be a standard way of pronouncing it - they only way I know is the way I do it. Please mail me if you agree or have a different pronounciation yourself. I'd like to know How many variations there are!
Lee-on-hart (wave file, 9K long)
Charlie L. (from the USA) pronounces it as Len-heart, as have all his family since his great grandfather emigrated in 1890.
I expect this page to grow!