Alfresco, some awesome sightings, and the two girls is incredible, I have seen blow jobs down a side street but never girl on girl action.
I used to try to go out in Sheffield most Friday nights some years ago and have seen some amazing sights, but never that many in the same night.
One which springs to mind, and it was in Hull town centre, I was wandering about as you do, when I spotted two girls who seemed a bit desperate but there was nowhere obvious to go. There was a little circular garden area with benches so I guess in the daytime people would sit there for a rest and look at