I recently read in Diarmaid MacCullochs 'A History of Christianity' that the pillar dweller and hermit, Simeon had a church built around him, almost like a "living exhibit in a Christian zoo". However this contrasts other sources which have the church as being built decades after his death (his death being in 459 AD and the church being built in 475 AD). Which of these correct? Any help most appreciated.
The text you have read refers to Simeon Stylites the Younger, who appears (according to this source and to a Life written around his own time) to have had a monastery built around him while he was alive. But as the aforementioned source says (as most other, apparently), the Church of Simeon Stylites the Elder was built as a posthumous memorial.