@bq - it'd be quicker to rip off the old plasterboard wall and re-do.You then get a nice even surface to tile on. Cutting and fixing pb to battens is a piece of piss and as you're tiling over you don't need to worry about taping and skimming, just wash over with pva before commencing tiling. Only area that will need attention is at the joints between other walls and ceiling. Tips, invest in a powered tile cutter table, get the joints spot on, and take your time with grouting
@bq - it'd be quicker to rip off the old plasterboard wall and re-do.You then get a nice even surface to tile on. Cutting and fixing pb to battens is a piece of piss and as you're tiling over you don't need to worry about taping and skimming, just wash over with pva before commencing tiling. Only area that will need attention is at the joints between other walls and ceiling. Tips, invest in a powered tile cutter table, get the joints spot on, and take your time with grouting