In my particular case, I'm positive the cross contamination came from touching. I had the stilton in a dedicated wine fridge and the provolone was in a completely different room, hanging inside of a container.
As for the Stilton making site you suggested, I have visited that site many times. I'm also trying to make the perfect Stilton and feel I am getting closer with each attempt.
On my last batch, I did give the cheese a very smooth surface upon removing it from the mold and this is causing a very nice rind to form.
I am also going to wait until the 4 week mark to pierce the cheese instead of doing so upon unmolding (as I did the last time).
The reason I'm not going to follow the Stilton sites instructions to the letter is because I am making a much smaller wheel than is commonly produced.
After molding, my wheel measures 4" diameter x 7" - 8" tall.
I made a lot of mistakes on my first attempt (not smoothing the sides, piercing too early, piercing too much and eating too young). Regardless the flavor and texture was absolutely fantastic, even though it was an ugly little thing.
Now back to the subject of cross contamination....
When I decided to make my first blue, I bought a wine fridge that I could dedicate to this one variety.
From what I understand, the biggest threat comes from actually spreading the mold through touching, although some claim airborne contamination has happend to them as well.
I have no experience with airborne contamination but I do feel that it could happen, especially in a small space. This mold really is very aggressive.
Keep us posted on your progress and please share any information you pick up along the way. So far this seems to be a pretty easy cheese to make or at least you get good results even if mistakes are made.