Many people goto Harrods / Knightsbridge in central London to spot (or hoon) their luxury cars. It makes little sense because the roads are slow moving, narrow and little more than a few revs can be done with no real feeling of speed.
However, some of the most exclusive and rare cars can be spotted here, particularly in summer where many people from the middle eastern countries bring their mega expensive cars over to enjoy the summer with.
For the best experience view this post on Liketu