I can’t help a lot but wonder if they aren’t the original tiles on the walls and floors of the bathroom, then they shouldn’t be considered common property…. Similarly if the membrane isn’t original but has been applied, like the new tiles, onto the common property, then it’s not common property either?
However, pipes and electrics will presumably cross into common property walls (those on the boundary of your property) so will need a resolution of the OC, and a special bylaw.
Perhaps get some quotes from some strata lawyers (plenty named on this site) for the special bylaw. You’d think it would be a pretty standard thing to whip up by someone experienced in that area of law….
There’s always safety in numbers, so are there any other owners thinking of renovating that you could join forces with?
Good luck!