Replacing old bathroom wallpaper with paint

[DIY10291]

The bathroom is half-tiled, half-wallpapered. However, it's been maybe 30 years, and the wallpaper is in bad shape.

I would like to sort it out myself. I think painting would be easier than papering or tiling. However, I'm not sure exactly what I need to do to get it into a paintable state. As you can see, it has peeled off completely in some places, so it shouldn't be too difficult to remove. But I'm not sure which parts are wallpaper being torn off, which are parts of the wall, and if there's anything else in there like a layer of old primer or paint or something. In the pictures, I don't really know what I'm looking at - there's some white powdery stuff, some bubbles, various layers, one of which is blue and hard to peel, and some pink in there too. I also don't know whether I'd have to steam it off, seal it (using Zinsser Gardz?), and if I can get away without skimming it/using polyfilla, if I'm not too worried about achieving an amazing finish (the rest of the house isn't in great shape either, but this peeling wallpaper obviously looks particularly awful), and can just paint straight on without primer (Bullseye 123?) - the paint I'm looking at (Zinsser Permawhite) claims no primer is needed.

Can someone please help me come up with a plan to sort this out?

 

[Bonni]

Pull paper off, sand walls. Fill holes, sand, and repeat as many times as you want. Brush on Zinsser Guardz, matt emulsion, and check if you need to do any more filling and sanding. If you, brush Guardz over the filler and apply two coats of soft sheen to the walls.

 

[Odds]

Maybe you find a pro to check the wall before you paint over it. They can advise you on the state of the plaster and whether or not a damp course will be advisable. Does it feel damp where its peeled from the wall? Is your bathroom subject to extreme condensation?
A job like this can be 90% preparation before you do any decorating.