Timber studs were not an option on this one I'm afraid. doing so would have left the boards covering the door frames, the stringers on the stairs and the timber that the hand rail is fixed to. removing the timber that the hand rail is fixed to would have been a lot of messy work, not to mention it would have left large holes in the walls as it appears to have been fixed with screws in to wooden blocks that have been driven in to the mortar joints.
the stringers on the stairs are quite narrow anyway, dot and dabbing has just about left enough of a detail on the timber that can be painted. battening the walls even with 2x1 with the state of the walls would have left the boards overhanging the stringers.
Thanks for the advice though, I'll bear it in mind for future reference