Geoff Higginbottom was doing some research, and was surprised that he couldn't find anything specifically marking 'St. Peter's Field' on or around the Free Trade Hall... until he was doing something else and found a little blue plaque in a doorway down a back alley. So the Free Trade Hall (or what's left of it) isn't quite on the site, it would seem, but close by.

I can't just recall where he said the plaque is to be seen, but I'll find out!