i've read quite a lot about this on the internet and realised its probably the wrong thing to do. however i thought i'd try it and see what it does as i'm not that concerned about things being perfect. i painted the new plaster area with 1/2 pva/water and its left a clear coat of pva, which is tacky but then shiny when dry. as a painting surface its very smooth and not absorbent. i painted some of it but wasnt happy with the way it was going on. its kind of nice when the walls absorb the paint, so you dont feel you're slapping too much on.
after i did it i thought it might be a bad idea and thought, well can the paint/pva be removed. well yes, it can, with hot water, a cloth and a lot of elbow grease. so i've got a small area back to plaster with the pva/paint gone. thats only about 1/4 of what i painted tho.
so i'm probs just gonna finish the painting leaving the pva on. if i could start again, id go with the watered down (but mixed well) matt emulsion