Can you recommend evergreen climbing clematis suitable for 1. planting in wooden trough in sunny (v. hot)courtyard [frost tolerant, if possible] 2. planting in ground, getting a certan amount of sunbut overhung by large plane tree
No clematis will do well in a pot in a hot sunny place, the pot is too restrictive and the soil is too dry. Make a hole in the paving and plant into the soil. You could use Clematis armandii, which is not totally hardy but tolerates quite a lot of frost.
The best bet for a partly shaded area would be Clematis montana.