Let them go to seed or cut them off ?
I was hoping Monty or Carol were going to tell me the answer to this question on Gardeners World last night. Did I miss it ?
I cut most of mine down, but save a few really good ones to let them set seed, then when ripe I scatter the seed where I want it to go - it usually produces lots of little plants that can be transplanted next spring.
Will prolly do half 'n' half.