[ViridianFan]

I think a few of the stings were footage of the balloon superimposed onto the landscape. The one over Edinburgh, the chalk giant and the white
Cottage. I had read somewhere too they had used footage of the balloon and superimposed that onto the landscape the balloon couldn’t fly over. 

The only ones I do w question if they are CGI are some of the special idents:
- the eclipse ident 
- the blue plant ident

I could never tell though if the 2001 Christmas ident if the balloon was CGI or not. 

The 1999 you can see it’s real footage of balloon superimposed onto the night sky, similarly the 2000 with Father Christmas dropping the present (although I’m guessing minus Christmas pudding jets) but it’s hard to tell with the 2001 as all rest is clearly CGI but you never zoom in close enough the balloon through the window.

Edit - should have been balloon not blow