Like you, I am fed up with campsis! I tried to grow them repeatedly in the UK but at the end of the season, most of the new growth tended to die back in the frosts of the next winter.
Near us here in France is an enormous campsis which grows along a fence by the main road. Every summer it's smothered in flowers.
Thinking we couldn't fail here, we planted a campsis about six years ago. It is in a shady spot beside the house, but more or less south facing. It finally made it up on to the roof last year (it's fifth year) but most of the flowers (about six of them) were on the lower stems. I expect the cold winter will kill off the stems on the roof.
All of this is basically to say that campsis need LOTS of sunshine and warmth to ripen the growth on which the flowers will be borne in future years. Without an exposed (to the sun) south or west facing spot, you are not likely to succeed.
I'd be interested like you to hear from anyone who is succeeeding with campsis as it's one of our most frustrating plants.
Like you, we are on heavy clay here. Perhaps that is a factor. What do others think?