Condensation problems

We have done a bit of work at home putting in new floorboards and repainting. Out the back of our house there is a large expanse of glass - windows and an area on the ceiling that meets the back sindows - about 1m x 7m which is glass.

The window panes used to be just stained cedar. We have painted them a gloss white (the wife used water ased paint, so not sure if that is a problem). The floor also used to be slate (on top of a concrete slab) so any condensation in the past we didn't really care about.

With the colder days here in Melbourne, there has ben a lot of condensation especially on the glass ceiling part. The drips from this are falling onto the new floorboards (not too much but which I am worried about this) and some of the drips are causing a stain on the white gloss paint.

Two main questions - is there anything I can do to ease the condensation problem? I know ventilation is the killer, but what can you do in these old homes?

Is there something I can do with the paint? Given that it has already been painted with a water based paint, am I up the creek?

Thanks in advance.