Sue Says
A really good plant for a north facing wall is the climbing shrub Hydrangea petiolaris although it is not evergreen. It produces large heads of small white flowers in the summer. Vigorous climber Parthenocissus henryana (Virgina Creeper) is also deciduous but produces amazing red foliage in the autumn.
Alternatively if you really would prefer an evergreen plant you could try one of the following:
Pyracantha produces white flowers in early summer and masses of colourful berries in the autumn.
Berberidopsis coralline produces red flowers in summer/early autumn
Lonicera japonica Halliana (an evergreen honeysuckle) produces vigorous growth with fragrant white/yellow flowers throughout the summer.
Pileostegia viburnoides produces heads of small cream flowers in late summer/autumn.
Ercilla volubilis produces pink-purple flowers in the spring
Akebia quinata has fragrant brown-purple flowers in spring followed by decorative purple fruits.