Actually, after a quick think it may even be the standard fit to angle the wiper wheelbox so that it points down towards the wiper motor. 2 countersunk setscrews hidden under the rubber inside the windscreen are the ones still hanging on the brackets and the other holes hold the wheelbox.
Design change at about chassis number 160,000 so those are earlier and for the wiper wheelboxes that have a rubber grommet rather than a chromed nut visible ahead of the windscreen.