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Our steamer belongs to my girlfriend's Mum, and she's being a bit funny about me loaning her Mum's stuff. However, I recommend picking up a large foam sponge and a bottle of wall paper stripper solution from Poundland. They have decent strippers of different styles too. The steamers can have a habit of lifting old plaster off the wall. A wet sponge is just as good in my opinion. If it's thick anaglypta or wood-chip, then perforating the paper can help too.
rodabod-
If it wood chip then try to scrape the top layer of paper that covers the wood chip off first, the backing is very porous and comes off easily with wallpaper stripper solution. The solution reduces the surface tension of the water making it 'wetter' or more able to soak into the paper. Some of them have an agent which acts on the glue to make it easier to clean up.
Airhead
Paper stripper