Hi Loz,
The first plant that came to my mind is the Montana Clematis...or any other Clematis for that matter.
I found this article on the web....maybe you might get some ideas:
Plants suitable to hide a wall -
Firstly, decide which way the wall in question is facing as this is imperative to know when selecting the most suitable plant.
North facing walls - the ground in front of a north facing wall will suffer from dampness and lack of sunshine. Some suitable varieties could be Clematis hybrids, climbing Hydrangea, Ivy, winter Jasmine or Roses (e.g. 'Gloire de Dijon', 'Mme Alfred Carrière' and 'Mme Grégoire Staechelin').
South facing walls - as these get plenty of warmth and sunshine dry soil could be a problem. Try Honeysuckle, Passion Flower or annual climbers mentioned above, such as Nasturtium and Morning Glory or Ceanothus, Mexican Orange or Myrtle which are more tender plants.
East facing walls lack sunshine and sometimes suffer from cold winds. Flowering Quince and Forsythia should be suitable and most Roses would be O.K.
West facing walls are probably the best site of all and, therefore, decorative shrubs and climbers such as Magnolias, Camellias, Wisteria, Honeysuckle or Clematis Montana would be ideal.
Happy Planting,
Annie