They do make a difference Yorkie but it needs a few applications if its bad, we use the weed and feed ones that really help the look of the grass as well.
Good luck thatruddyvicar, we have them as well, def dont leave them flower we did a few times last year and that was a big mistake!!
We tried torching some growing on the drive, they came back and it was time consuming, so we give up after 2/3 attempts. It wasnt as much fun as I thought it might.