Home DIY

@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

It's only a kitchen splash back, about 60 cm high, by 4m, not the whole wall.

@Dammit,
Did I ever tell you my technique for getting a perfect plaster finish on remedial work?
Plaster the dodgy area wall until it is either level with or the existing plaster, and the when it dries get the black and decker power sander on it until it looks flat and smooth :-)
Power tools > hiring someone who can do a proper job in the first place!