I may be entirely wrong on this, but I believe that the approach control suffixes are as follows:
Approach - Procedural Approach Control
Radar - Approach Control with the use of ATS surveillance systems
Director - Approach Control for arrivals only with the use of ATS surveillance systems
There are several exceptions to this rule (like I believe IOM use "Approach" even though they have a ATS surveillance system but this is due to a limited service due terrain, etc) but most follow the convention above.