You can cut these back now if they're getting out of control, but you wont get any flowers next year, cut some shoots right back, and leave others a bit longer, until you get the shape you're looking for, take out any dead, diseased, or crossing branches completely, Derek.

I tend to leave everything on....even the old flower heads, they are supposed to protect the new shoots from the cold.
I,d take off the ones causing a problem and leave the others until spring.....

or when you have pruned them use some form of plant ring Y stake to keep the plant supported.

I agree with Pamg. I leave on the old flower heads until next year so I would only trim what is necessary

I agree!, but leaving the flower heads, and doing the usual prune, is not going to stop them from being straggly, and blocking the path, they therefore need a more drastic prune, Derek.