Strip or overboard blown lath and plaster walls

[Gsquared]

I have a small original loft room in my Victorian house that has two brick walls (one external, one party wall with neighbour's unconverted attic space) and two lath and plaster walls along the roof cavity space.

The plaster on the walls has been held together by wallpaper from before we moved in which is now peeling. Having stripped some off, the plaster is badly cracked and bouncy in places. The chimney breast seems to have been skimmed.

Is it best to overboard with insulated plasterboard (don't mind losing the space) or strip everything back to the rafters/batons and insulate, plasterboard, skim? Given there's a cavity and then the roof along two sides I don't know what's best.

Note this room gets ridiculously cold and is up a steep and winding set of stairs and the main staircase so removing waste will be a nightmare. Equally, if we overboard, will that just cause mould and damp problems given the existing plaster is compromised?

This room doesn't need to be perfect given it's not used all hours of the day so I'm not looking for a super high quality solution, just something serviceable and affordable.

 

[blup]

You could insulate the cold wall behind a built timber frame, and board the rest

 

[23vc]

overboard the lath ones, life’s too short to strip them (dirt, effort, waste removal)