Re-skimming Existing Plasterwork
If the existing plasterwork has not blown (de-laminated from the original substrate) existing plasterwork can be re-skimmed using a sealer and an appropriate finishing plaster, hairline cracks are generally due to age and shouldn’t be a problem.
Over boarding an existing lath and plaster ceilings with plasterboard is a better option to avoid any future movement on badly cracked ceilings.
This is a relatively inexpensive way of achieving the look of a freshly plastered walls and ceilings.
Textured Walls and Ceilings
Restore textured ceilings and walls back to a smooth finish using pva and a coat of carlite bonding to eliminate the texture then apply an appropriate finishing plaster, you will then have perfectly smooth finish. Once dry, wallpaper or emulsion paint can be applied.