Redalways:

I take your point -

but surely if the Post Office have been notified that you have made alternatives to "return to delivery office" available, they have no excuse to leave your parcel out of the van or to say it isn't worth their while to take it to somewhere they can't deliver it - because you've made sure that they can!

And you have better grounds for a complaint that will stick if your specified wishes are consistently ignored, by management, postie, whoever.

Just offering a way to get your parcels, and if not, get whoever's responsible.