Hardy geraniums?

Have a look at the website of the Perennial Garden, St Davids for suggestions. They specialise in plants that will grow in windy places.

Lily of the valley will help to hold the soil if they are happy, but they only flower for a short time. Epimediums are good for ground cover in shade. Viburnum Tinus is a good reliable evergreen shrub that should do well and you can clip it if it gets too big. Pulmonaria like shade and are in flower now. Dicentra will follow on, and then the hardy geraniums.

Walk round the boundary on a sunny day to see if your head catches the sun even if your lower half doesn't. You can make a plot look much sunnier than it is by planting something tall that will emerge into the sunlight.

My good old standby Euonymus fortunii is always bright and cheerful all through the year, and the brightest is Emerald 'n Gold.

Ferns might do well - there are even one or two varieties that will grow in dry shade, though most prefer moisture, as do hostas. Heucheras are available with lots of different patterned leaves. Fibrous rooted begonias are great for cheering up a dull north facing space, though you have to replant every year.

There are one or two climbing roses that will be happy on a north wall - can't remember the names but I do remember at least one is a lovely yellow. Might grow on an arch?