Because your garage required planning permission in the first place, its alteration would not be covered by permitted development rights. The alterations don’t sound at all contentious, but you’ll need planning permission for them. The conservatory roof is a similar scenario. Because it needed planning permission then its alteration would need permission too. Putting tiles on the roof to match the rest of the house doesn’t sound contentious planning-wise, but you might want to check the pitch is adequate for tiles.

Mike Dade (Build It Expert)