Repairing internal plasterboard wall in flat

[DiyNutJob]

If the internals plasterboard walls in a flat are damaged by water and I want them replaced, can I hire my own contractor to do it? I understand the plasterboard walls are considered part of the building structure and therefore owned and insured by the freeholder. Being a leaseholder, can I replace the plaster walls without asking? The walls could be stud partitions, or dot and dabbed. The walls could have electrical outlets on them. Would it require involvement of an electrician?

I think I have a share of the freehold. Does this change anything?

 

[DiyNutJob]

Out of blind luck, I managed to have a surveyor to look at the damage for free. To avoid impoliteness, I did not ask him for his credentials. From what he said, repairing the plaster wall through replacement is not an alteration and therefore doesn't need permission from the freeholder or the building regulators. Personally, I would inform them anyway.