100mm rockwool vs Insulated plasterboards on Brick wall

[Bentley]

I have a brick wall without cavity and looking to remove the plasterboards currently on battens. 

 

What is better and economical to put up cost wise rockwool and plasterboard or insulated boards. In terms of time taken to put up and skim

[Mr Punter]

Rockwool is about half as thermally efficient as PIR, so would you need twice the thickness for the same insulation.  Insulated plasterboard has either PIR or EPS.  The EPS is between rockwool and PIR for performance.

 

If you have space you can build a new timber wall and insulate it.

[Crofter]

How is the existing plasterboard attached? Is it dot and dab on to the brickwork, or are there timber battens?