AusBonsai

English elm ----- 1/3rd leaves are still green , 2/3rds brown - is it bad to defoliate now and force hibernation? i sort of have to push it because of work commitments

Wondering why you want to force dormancy? Why not let the tree go through it's natural cycle in the appropriate time frame?
In most cases defoliating (or pruning) this late will not bother to grow new shoots and so, essentially enter dormancy earlier than normal. There does not seem to be any long term problems with doing this.
Occasionally, or if you get timing or weather a little wrong, The tree will just send out new shoots. I had this happen with a batch of Japanese maples. Those trees had healthy leaves all winter. I was concerned at the time but they all reverted to normal cycle the following Spring.

My guess is that it would be safe to defoliate your elm now.

thanks shibui - I am time poor at the moment so I need to move them along a little while I have the opportunity