To answer your questions AMS:
Students per instructor - There are times when there are quite a few students.. However the head of training does a good job of spliting them up evenly. At the most busy time I was there my instructor had myself and 4 other students if i remember correctly. However 2 of them were conversion students so they didnt stay too long. You have your instructors complete attention.
ILS Approaches - LGTS is about a 40 minute flight in the DA42, which is where you do the ILS approaches. Its a busy airport so you get radar vectored in which is a nice experience. This airport has two runways, 16/34 and 10/28. 16/34 is used 99% of the time and it has an ILS on runway 16. 34 has a very interesting VOR/DME appraoch. I did 3 ILS's in my IR on the airplane.
Yes you do fly in the airways. On every single IR flight.
I did my training there from september until december 2010.
Some additional information that I found very important at Egnatia. There are no hidden costs what so ever. What they quote is what you pay. Daily expenses (food, drink...) are very cheap, so you wont be using up alot of money. Aircraft are brand new, with all instruments working at all times. Maintenance guys are very kind and professional and wont hesitate to help you out if you need anything, or to answer a question you may have.