Have not studied the JAR nor ICAO rules yet but FAA says a circling approach must provide a minimum of 300 feet of obstacle clearance within the circling approach area. The size of this area depends on the category which the aircraft operates.
Category A= 1.3 mile radius
Category B= 1.5 mile radius
Category C= 1.7 mile radius
Category D= 2.3 mile radius
Category E= 4.5 mile radius
Digging deeper into my FAR/AIM I get this from CFR Part 91:
"An aircraft can only fit into one approach category. If it is necessary to manoeuver at speeds in excess of the upper limit of the speed range for each category, the minimum for the next higher approach category should be used"
So a Cat C aircraft would become Cat D, and so on.
But I do think Citation2 has a point.(règles DGAC-JAR je suppose??)