Hi Bradley
Yep that looks like a right old mess and cant say I blame you for not wanting to strip it all. Couple of options I can think of.
1) Depending on the set up and whether theres enough space you could think about re plaster boarding over the whole lot. It really depends on whether it would bring the walls out too far behind the bath and wc etc but it would be quite a quick way to get a nice new flat surface to work on
2) How about just getting off the loose stuff then sealing it and skimming the whole lot. Provided you seal it all properly it should skim ok and agian you'd then have good surfaces all round.
Failing this then it's going to be a question of stripping all the paper (I know that's not a good thought