@SpeakingFranglais
Score the walls with a Stanley knife in diamonds like you might a ham or piece of squid 😂
Go round and soak the walls then use the steamer and good quality scrapers, it should come off easily in diamonds.
Old school Decorator’s daughter
From recent experience, this is right
Soaking the wallpaper (with a sopping sponge w a drop of Fairy) made a huge difference to how easily the paper came off. I'd try a bit without scoring as you may be lucky and it comes off in sheets, or if it doesn;t then you can score
What worked for us: soak (go round room), soak again, then steam & strip
One tip: don't hold the steamer down too long, as this is one of the things that makes plaster crumble