Well it might sound obvious, but for starters I'd remove the brown leaves and put it in a bigger pot with some new compost and see if it cheers up.

</p> Thanks for info Steragram I will give it a try from Budd<p>

It seems to be what they do!
You end up with a long stem with leaves high at the top, one got too big for our conservatory so we cut it off, it is now multi headed and we grew another plant from the removed head

I would agree with Steragram, put it in a larger pot, but as with any plant that forms a woody stem, it will gradually lose its leaves from the bottom, even evergreens lose leaves, but continually, rather than in 1 go, Derek.