Shut all doors and windows to trap moisture.
Use a perforator to pincure the paper.
Sponge it all down a few times allowing 10-15 mins a time for the water to soak in.
Get a 4" wallpaper scraper and don;t be frightened to use a wallpaper steamer.
To stop the top layer of plaster blowing, don't dwell on one spot for too long.
Expect the plasterwork beneath to be poor (why else would people have used woodchip everywhere?).
When you have stripped the walls and washed them down with sugar soap, repair the imperfections with Gyproc Eazifill jointing plaster. It's easy to use and doesn't go off as quickly as other plasters. It's very much like Polyfiller, but you mix much larger quantities.
Allow to dry and sand flat.
Apply a mist coat of slightly watered down emulsion then decorate as usual.