Recommendations for a climber through a hedge?

elderberry

The key requirement here is the climber needs to be vigorous enough to make a good showing between the hedge's cutting times.  So, for example, while a Montana might be good, I'm guessing other clematises wouldn't be able to make much impact. Bindweed already does very well on the north-facing hedge I have in mind, so maybe the purple version, Ipomoea purpurea, would do well? We typically have -5c in the winter, getting down to -10c every 5 years or so. I'm on alkali, free draining chalky soil in SE England.

Ceres

In my experience, you can't beat Lonicera Japonica Halliana for rambling through a hedge. It is rampant, takes over, and smells divine.

Posy

A great deal depends on whether you are a tidy hedge person who trims and shapes, or someone who likes a loser, more natural appearance. A mix of dog roses and honeysuckle in a tall, spreading hedge is beautiful, fragrant and wildlife friendly and really only needs a cut every couple of years but it won't fit into a small suburban garden.

Hostafan1

What sort of "hedge" do you have? Wild and woolly or trim and tidy? 
Some climbers can have a detrimental affect on their host.