Internal wall insulation method

[whiskeyfrank]

HI
I have a 1900 solid brick house, damp proofing done and no issues.

I want to insulate a few walls in different conditions, internally and thinking of the following

(plaster still in place and solid as a rock) - Batten the wall with 2x1 infill with cellotex/xtratherm or rockwool panels at 50mm thick then plaster board.

Questions
Is this enough or should I go thicker and do need a vapor barrier on top of the insulation and/or under battens against the wall?
One wall has no plaster is the process the same?

Thanks

 

[foxhole]

No battens, just insulated plasterboard , foam adhesive, no vapour barrier.

 

[Bouy]

Have a look at kingspan k118 brochure for info on fixing too solid walls