If the areas are larger, then Zinzer bullseye 123 which will both stop the pulling and help bind the paint over the filler.

also, when i come to put a colour on, which paint should i use, has anyone used this godforsaken polycell 3 in 1 base coat? If the areas are widespread and could be coated easily then thinned undercoat, if they are so wide spread that you would be painting most of the wall then primer.

Where to use

It's difficult to decide which way you should go as we can't see what you can. I have dry lined both our utility and kitchen and have (in the utility) cut out a section of plasterboard and refitted, filled with easy fill, sanded and painted you'd never know it was done. Now dependant on the area you are filling, when you paint over you will probably see pulling of the paint and the filler will absorb the paint more than the surrounding area. This can take 4 to 5 coats to cover up. If it's smaller localised patches take a weak mix of oil based undercoat thin with white spirit and brush over the filler allow to dry, mild 240, 320 sanding and emulsion. Really needs to be oil undercoat as you're introducing a barrier to the filler to kill it's absorbency (although Zinzer Bullseye 123 is a 'wash your brushes in soapy water'. But I think the clues is in the soapy water bit).

Bullseye 123 isn't cheap but the finish I got was really impressive, I did patch some filler in a ceiling with undercoat and it's just as effective, don't be put off by the immediate result of painting emulsion over the undercoat (if you go this route) as the patch will take longer to flatten/dry as it isn't being pulled by the patch below, it will look patchy but will flatten out fine. i can't sand it as i have just cleared the whole house of dust from sanding elsewhere, the only thing i can think is to get it skimmed...turning out to be a very time consuming and expensive mistake I'd use Easy-Fill or Easy-Fill 45. You can get it really creamy and smooth, apply over the patches with a proper trowel just as you would with plaster. It's really easy to sand as it's soft, I'd take the worse off with say 120 grade and finish smooth with a 240 or 320 grade. Just work slowly and evenly. If done properly you won't see a thing.

i did ring polycell and they suggested it was incompatible with other brands outside polycell/dulux Don't have a photo of that actual part but I'll happily get one tomorrow if you need it. Here's an example of the finish you can achieve with Easy Fill.....