The circling minima you want is the one for the instrument approach you will fly, in your example RW 36.
PANS-OPS criteria is that it is based on a 4.2 NM arc from each runway threshold and the arcs are connected tangentially to produce the circling area encompassing the whole airfield. The area is surveyed for obstacles and a circling minimum calculated which will give a minimum circling height of 600ft with a minimum obstacle clearance within the circling area of 400ft (for Approach Cat C aircraft). Thus the circling approach for the other end, RW 18 will usually be the same. However there may be different minima for circling in different directions, for example circling to the East of RW 36 may have a circling minimum of, say 1000ft while circling to the West may have a higher or lower minimum because of the obstacles in the respective sectors.
That's my understanding, anyway.
HTH,
WS