Hi again
Although Chinese Elms are often sold as indoor trees, they are far happier outside. Find a sunny spot (i know this is difficult in our british summer
) in the garden and leave it outside. There should be no need to bring it in overnight. My Elms stay outside all year round (except for the few days when we get heavy frost (below -7C) when they go in to an unheated greenhouse) and they show no ill effects.