North Facing

Even hostas benefit from a bit of shelter from strong wind - is it possible to plant or erect something at the end there the prevailing wind blows from just to moderate it a bit?
There is the invasive euphorbia robbiae which will grow in dense dry shade and I imagine it would grow just about anywhere but its not one of the prettiest plants. On reflection would a whole row of ferns suit you, possibly all the same variety to look like a little hedge? You can get evergreen ones, have a look at the Long Acre Plants website. They will also give you advice if you email them.

Providing one of the walls is yours, a climbing hydrangea would be very happy to face north, and after a couple of years will cover as much of the wall as you let it.
Hydrangea.petiolaris is its name, large white lacecap flowers appear in June.
Another shrub that will grow anywhere is Buddleja, but you don't say how wide the passageway is, as these can become very large.
For annuals, Calendula, pot marigolds, will cope with poor soil and shade. Also Cornflower,( Centaurea ).
Foxgloves and Delphinium can cope with shady sites, they do in our garden. I have been told that Mimulus, will grow easily in North facing sites, but I have not tried it. Forget-me-nots will grow anywhere, and reseed every year, also poppies.
These are just a few, keep trying, and good luck

Would the wind be a problem with the tall flowers though?