I'm currently putting up stud walls in the downstairs toilet, The plasterboard sits together quite well. I'm wondering if I put joint tape up, then lining paper plus the wallpaper I'm going to be using, will this be enough? Or will I still have to using jointing filler as well. Thanks
Do it right and get it plastered. You will find yourself in trouble with the plasterboard if you decide to strip the paper in the future.
Tape the joins and fill with a joint filler such as easifil, when dry sand down to smooth finish, I would apply Zinssser Bullseye 123 over the whole wall to seal it then line and use the wallpaper of your choice. Most wallpapers today are easy to strip off plasterboard as they peel away from a backing paper. It is important that you seal the plasterboard though.