Hello,
Thanks for your question about a suitable climber for your west facing wall on constantly damp, clay soil. I have to admit, that I have been stumped by this one!
There are, of course, climbers that will cope with the damp soil and poor drainage but they don’t necessarily have red/bronze leaves, nor are they restricted to a maximum height of 3m approx. When I say this I am thinking of some Clematis and Ivy for example. It has to be said, that 3m is actually quite a restricted height for a lot of climbers, and should you plant one you might find that you are constantly having to prune in order to restrict the growth.
I am going to suggest that you consider the following shrubs, which might be more suitable in the circumstances. They include some ‘wall shrubs’ that are ideal for growing against a wall, there are also some shrubs that could be pruned and trained to encourage an upright habit to cover the wall. Consider:
Ribes (flowering currant): Various species and cultivars with deep red or pink spring flowers.
Viburum opulus: This shrub is native and produces good autumn colour and berries.
Cotoneaster: Various species and cultivars will do very well against a wall on damp soil and produce good autumn colour and berries.
Corylus maxima ‘Purpurea’: The Hazel with deep purple leaves.
Cornus alba cultivars: The dogwoods have upright, deep scarlet winter stems.
Chaenomeles: There are a good selection of Japanese Quince that make excellent wall shrubs, red and pink flowers available.
A far more exciting and interesting plan would be to design a herbaceous border backed by the wall that could be specifically themed for moisture loving plants like Ligularia, Rodgersia and Hosta. Some of the herbaceous plants would be nearly as tall as you have specified to hide the wall eg. Ligularia ‘The Rocket’
I could give you some further suggestions if you decided to go down that road.