Explode the block and edit the sketch. Now insert a sketch point at X and Y coordinates (59,59 in this case). Convert the sketch into the block and set that point as insertion point
Edit the block and click on insertion point. Now set the required coordinates and exit block edit.
I have learned that a block is a dumb shape without relations or dimensions, and when it is exploded it becomes a totally undefined sketch and SW cannot begin to calculate full definition; it must be done manually. That is a lot of work over many blocks, so I found another way to achieve my desired result.
Placing a ref geo point at the centre of the end face of the section puts it at the centroid of the section. A ref geo axis through that point is a suitable handle for mating the part.