Mine are floweless too at the moment I,m wondering if the position of the pot means they are not getting enough sun?

I guess you are growing cosmos from seed each year as I only know it as an annual, unless I am wrong and there is a perennial variety? If it is an annual then yes I would say it needs fresh compost each year. I wonder also how well it would be suited to growing in pots as I always plant my cosmos in the open ground where it grows well. Having said that mine have only just started to flower within the last few weeks too so I am sure there is time yet, maybe give them a feed, or would that just encourage more foliage?

Yes I grow them from seeds and they usually put on a good display but I must admit I have not changed the compost for a few years given the size of the pots so next year I will have to change the compost which is so expensive or plant something that won't mind used compost what do you think I have added a few photo,s to the question for you to see :-) thanks

Mine in pots aren't flowering yet either,Kidsgran..but the ones in the borders are..The foliage on mine in the pots,isn't as bushy as your's but my,they are tall ! I should have taken the tops out earlier I think..they look out of place with the bedding around them..ah well,I guess they will flower at some point,as will yours :o)