Thanks again John!
I was afraid it would be necessary to leave open that air contamination route, and it seems you just confirmed my fear.
I noticed there are previous threads about the issue, but it seems to me it is unclear whether the p.roqueforti can go airborn or not. Well, I guess it's a risk that not many are willing to take considering the large amount of work they've done with their other cheeses.
Having eaten a lot of store-bought blues though, I'm wondering why those never cross-contaminated my other cheese. Maybe it's different because of the flipping and continuous touching, moving around (maybe that releases particles that float about, I dunno) or just poor hygiene when flipping different cheeses.
After all, I never touch my store-bought cheese unless I'm putting it into my mouth...
This really keeps me puzzled, since I soooo want to try a stilton, but also want to eat my Gouda and coming Havarti without p.roqueforti in it. No chance of getting another cave any time soon.