
yes, there are gorgeous Chinese rowans that bear beautiful white berries or white flushed with pink.It depends where your friend is, but there is a fantastic arboretum at Howick in Northumberland that specialises in trees from the Far East and for its size has to be one of the best in Europe. I've just checked their website and they have lovely photo of a white rowan on their website
http://www.howickhallgardens.org/thearboretum.php :-)
Another fabulous place to go is the Sir Harold Hillier Gardens in Hampshire--and if your friend is in the 'middle' of the country, there isn't much in the world that can beat Westonbirt, the National Arboretum at Tetbury. HHG and Westonbirt have truly excellent nurseries that sell out to the public...and Howick donates plants for a church sale each year--worth the travel any day.
Sorry to be a tree bore, it doesn't take muc to get me going :0.