PolkaDot, if I were you, I'd spend the money on Colortrend paint for the 'public' areas of the house (living room, kitchen, hallway). Leave off painting upstairs for six months if you have to, until you can afford the better paint.
For me at any rate, the labour is the biggest part of the job; I'd sooner wait until I had the funds, rather than do a cheapy job now & have to do it all over again next year.
Edit to add: Colortrend do big buckets of what they call Ceiling Paint. Its a flat matt white finish, covers very well and would be an ideal undercoat for new plaster. You could paint upstairs in this and then leave it alone & it'll look fine till you can afford to paint the final colour.