Winter gales, exposed position, not much choice then, really - have a look at Prunus 'Otto Luyken', evergreen shrub, quite tough, only gets 3 feet high. Mahonia aquifolium's another evergreen low growing shrub which has yellow mimosa like flowers in early spring. Neither of these could be said to fit the description "cottage garden" - but then cottage garden means lots of flowery plants in summer which then disappear completely in the winter, leaving nothing but bare ground and dead growth, so a combination of plants is usually better. Given your situation, it might be better to restrict the fragrance requirement to stuff you grow for the summer only, with things like ten week stocks, etc - a wall of 3 feet is too low for honeysuckle, etc.

You could try a passion flower along the wall? or summer jasmine also plant arum lilies and day lilies against the wall, how about various ferns which give beautiful shades of green, try a few plants at a time to see how they fare, that is the only way to test then out.

A variegated Ivy would look nice creeping over the wall and give it a pretty background colour for subsequent plants. Obviously no scent but then you would have it all winter too............