evergreen or semi evergreen to cover a wall approx 3m wide by 2m high

Euonymus - 'Silver Queen' or 'Emerald Gaiety' are good varieties - both are very tolearant of a wide range of soil types and aspect

Large leaved ivy. There are some lovely ones showing marked variegation. Of course, I cannot think of their name at the moment. Sorry.

sir edmund hiliarus

Trachleospurnham jasmanoides

richly scented too..

Cotoneaster horizontalis has nice berries.

My choice would be Stevebuk's above - Trachleospermum jasminoides, though you might need two or three to cover the width of the wall adequately; you don't say which direction the wall faces, whether it gets east or northerly winds in the winter - that can make a significant difference to what you decide to grow there. and whether it's shaded - there's also climbing Hydrangea for shade and Actinidia kolomitka for a sunnier spot, but these two aren't evergreen. And by the way, I'd ignore Chitching's comment Sir Edmund.. don't think he/she knows any plant names but wants to say something ....!
If you're going to choose an ivy, pick a Hedera helix variety - don't choose H. hibernica or H.colchica - they get huge, far too big for the space you have, and H. canariensis (variegated, red stems) is not as hardy as the others.