I can't be of help with advice on general care, or good specie choices. Because your space gets quite dry and warm, I presume you will be watering or misting regularly? Maybe (some possible ideas with your branch) you could cover your hardwood branch with tree fern which might/or/might not work for moisture retention. Another possibility would be to use epiweb/hygrolon. This product does very well with 'wicking' water. It also does a very good job retaining moisture with regular misting if not used for 'wicking'. Another suggestion (has worked well for me in the past) is to tightly wrap the branch with long-fibre sphagnum. With regular misting, it too will retain moisture fairly well.

Thanks O2tiller - I had never heard of epiweb but looks like it may be the answer! I would be regularly misting but couldn't do it so often that I could keep normal substrates (such as moss) damp. I think the epiweb, perhaps with a moss over the top, might be worth trying (its not too expensive if it doesnt work).

Dont forget critical air circulation

Yes, conservatory is a frequent 'walkway' with big doors either end so air circulation shouldn't be a problem, especially March-November.

I have looked in to the hygrolon, and it does look good. I think if I could establish a moss on it, then that would act as a good mounting substrate for some bromeliads/epiphytes giving them not only something to 'grab' on to, but also raising the local humidity.

Does anyone know of a moss that would work well - conservatory is frost free but cool on cloudy winter days?