inside is better normally as long as its visable otherwise the next engineer along with notify it as not bonded.
im supprised you have come across a sparks who knows the regs, i told the sparks on site today you cant enter a meter box from the back with his earth cable (drill a hole where he likes) and he looked at me like i was talking out me hole. Wont think that way when the grid want £1000+ to change the box tho..........