The Airbus flight safety magazine,
Safety First carried an article in the July 2012 edition entitled "Preventing Fan Cowl Door Loss".
http://www.ukfsc.co.uk/files/Safety%...uly%202012.pdf
It mentions that there are more instances on the A320 than the wide body Airbus types, probably due to the low level of the cowling latches meaning thay are missed. It also empahsises the importance of checking the latches during the crew walk around check.
An article which will soon be required reading in BA I think!