Insulation panels and plasterboard

[koomber]

I'm looking to renovate my bathroom and am installing 25mm insulation board and 12.5 mm plasterboard on top.

I've been advised by the supplier that illI be okay to install the insulation on top of the existing plasterboard, securing to the existing battens through the plasterboard.

However the walls aren't plum so I'll need to fit additional battens to get it sorted again, the lad said that would be okay to just go on the board and go for it.

I'm not entirely convinced, but it would save me a bit of extra work. Any thoughts?

 

[koomber]

I'll add that the boy who did the plastering rip down the old plaster leaving the lath up and plasterboarded onto that...