Insulation in external walls

Hi all first post so be gentle.

Have stripped back all internal lath and plaster off the external walls (back to the brick) after repairing damp problem. How best should i batten, insulate and plasterboard these walls?

Whats the best combination? A friend has said batten from the roof joist to the floor joist, put in glass wool and plasterboard over.

This doesnt sound right to me as the glass wool would be pressed against the external brick work (would that not cause suck up any condensation?

Im lost

What was the original damp problem that you fixed? Insulation should not 'suck up' condensation, you should have a vapour barrier of either polythene before plasterboarding, or foil backed plasterboard.

Having said that you should not have any condensation if the room is adequately vented.

It's not unusual to see insulation up against exterior brickwork, good practice to leave an air gap though, you could just get insulation backed plasterboard and dot/dab it to the wall. Mechanical fixing is usually used as well as the adhesive.

The damp problem was two fold ..... lack of underfloor ventilation (suspended timber) with a high water table and also poor installation of the flat roof (whole house is flat roof and we are currently converting to pitch)

So what would be the best option? i want to leave an air gap but want to be well insulated as well?