Hi Dave,
I currently keep my Chinese Elm in a greenhouse with a heated bench as I have heard they shouldn't be kept indoors for long lengths of time (mine was indoors last winter and was ok). I think their lowest temperature in 7c. It seems ok at the moment. Where are you keeping yours? Is it indoors? How often do you water it? Also, if they are kept in a colder location, they will lose their leaves.
Try this link: BCI Species Guide - Chinese Elm
http://www.bonsai-bci.com/species/elm.html
Articles
http://www.evergreengardenworks.com/articles.htm
Rachel