This McDonalds restaurant was once the famous Chelsea Drug Store (as mentioned in the Rolling Stones song You Can't Always Get What You Want). It was the record store where Alex picks up two girls in this movie
The tunnel where the tramp is beaten up was filmed on location here in Wandsworth, London. It's the southern tunnel under the Wandsworth roundabout
The tramp gets his revenge by beating up Alex under the Albert Bridge on Chelsea Embankment