Ulmus Parvifolia and frost
 

I posted a message a while back about my Ulmus Parvifolia which was
losing leaves. Lots of helpful responses at the time, including the
suggestion that the tree should spend some time outside during the
winter.

I'd interested to know what to do about frost. One of the posters in
the earlier thread suggested that the tree should spend a period at 0
to 15 degrees C over the winter. The temperature here in Southern
England often drops below that at this time of the year - should I
protect it against frost (with bubble wrap, for example, which we use
on our ferns) or even bring it inside when the temps are heading down
to -5?

Thanks in advance for any help you can give me with this.