Hydrangea petiolaris takes a few years to get going but grows huge in time and although self clinging does not damage the wall. It is really magnificent when mature. The ideal choice for a north wall.

Thanks so much, we already have a hydrangea on the wall but it hasn't got going yet - maybe 2012 is THE year!!!

Euonymus varieties 'Silver Queen' or 'Emerald Gaiety' are self clinging when planted against a wall or fence

Although not a true climber, try Chaenomeles (Ornamental Quince), needs to be attached to your wall, but will flower early in the spring and able to withstand the ravages of winter.

how about Clematis armandii?

Seem to remember there is a yellow climbing rose that does OK on a north wall - perhaps someone on here will remember what it is?

I think that the rose 'Golden Showers' can be grown on a north facing wall, although I've never tried it.

Many thanks for such helpful suggestions. Might have to go for one of everything as it really is an ugly wall!!! Nice to hear that there is a climbing rose that would be happy there.

I grow the rose Golden Showers on a north wall and it has done very well over the years.