C'mon pilot's it's the law!
Rules of the air No. 19 (I think).
Right hand traffic rule. An aircraft which is flying within the United Kingdom in sight of the ground and following a road railway canal or coastline or any other line of landmarks shall keep such line of landmarks on its left:
Provided that this rule shall not apply to an aircraft flying within controlled airspace in accordance with instructions given by the appropriate air traffic control unit.
At Bristol the visual approach and departure routing is along the A38 so far as I remember. There's probably lots of others.