fixing curtain poles to plasterboard ceiling

[littlemouse]

I have looked for similar queries but can't quite find an appropriate answer. Here is the problem:

I am having to fix a curtain pole to a hollow plasterboard ceiling. I can't screw it in to the window frame or the wall because our landlord has already fitted wooden blinds that we can't remove. On drilling the holes for the screws I found that two sets of holes are into the joists to which the plasterboard is attached and the other two corresponding sets on the opposite side just go straight through the plasterboard and subsequently there is nothing to screw into. I don't quite understand how this can be as I thought one joist ran from one side to the other.

I have been looking at spring toggles and want to know if these are the correct items for this job or if I should be using something else?

I am a bit worried that the plasterboard is not in good condition.

[moger4]

the best way to do this would be to fix a batten to the cieling , maybe with a nice edge painted , and then fix to this , fixing it secruely to the joists