Hi
There is a great description by Gosling on http://www.howtomendit.com/answers.php?id=91950, I just wanted to add that the genuine part number is C00095566. They can be found more easily using this as they come in a kit. I have found it slightly cheaper on http://www.yourspares.co.uk/Product.aspx?Product_ID=74859
Sam, April 2010