I am not quite sure but I think this is it:
After the concert the people that want to stay behind and meet him go round the back to the stage door. That's pretty easy to find just go round the back and find a door with the words stage door on it, or words to that effect!
At Brixton after the stage invasion of Lollipop I don't really remember what happened, I think the people go off the stage because I don't remember them being there for the Relax encore, in fact they weren't there for Relax.
Hope that somewhat clears things up, despite my rubbish explanations!