Nadeem
What's the ICAO Disp licence? Do you mean the Flight Operations Officer Licence issued by other ICAO states except United States FAA?
Smohamed:
Sheffield is a very good school in USA for FAA DISP Licence and I believe it's worth to take the course in Sheffield, especially if you are looking for DISP job in USA. Of course it's seldom for any the DISP Licence holder to take the same course in different schools and actually it's hard to compare all DISP schools in USA without taking the same course among those schools. But according to comments from many people in this forum, and also guys from airlines, Sheffield is the best.
If you took the Sheffield 6 weeks course, it's better to get a latest FAA Test Prep (from Gleim or ASA) and study it well before the beginning of the course. Good school just let you to study that by yourself. Worst schools use the TEST Prep as theory teaching base and which is not a good practice.
I believe if you are loking for DISP job in USA, of course you have to take the course in USA. But if you are looking for jobs in Singapore or UAE, may be it's a good choice to take the Jeppesen courses in these 2 countries.