Hi ReadyAyeReady,
For future reference, it would have been better that you posted this second question in your original thread. It makes for better organization on topics.
I also studied outside the country like you for a couple of years, and I have been going through the same security sweep that you will be doing. I did a fair bit of reading into this subject and really exactly what happens in certain areas of these security sweeps is secret and no one really knows exactly what goes on. Certain information about the clearance is kept secret so that 'baddies' will not be able to think of ways of getting through the system undetected.
The main difference between this clearance and the normal clearance is the amount of information you give on the form. Such as listing all your family members and thier contact information, plus plenty of other stuff.
At one point they will contact the UK to confirm and exchange information (exactly what kind of info I don't know). It is good that you studied in a NATO country, as they have an agreement to pass information like that through computers etc. So that will speed things up.
It is possible that they may contact anyone you listed on the security form at some point (That may include your prof. in the UK if you listed him) But due to the processing times, I suspect this would only happen if there are indications of problems or they only do it to a certain number of applicants. If they physically start phoning people or visiting people to talk to them about you, then you could be looking at long wait (13 months at worst). If there are no snags, the average is supposed to be about 4 months.
I am currently in month 4 of my sweep, so I am half expecting it to come back within a few weeks. Unless they start contacting people I put on the form, in which case I can expect to wait a lot longer. So far, no one I know was contacted.
Hope this is of some help.
Pieman