It might be cheaper to do a worm count with the vet, Minster Vets do one for £23.02, rather than routine worming. I have 12000 free range chickens and have not wormed this flock at all, i have had them for over 40 weeks and only done 3 worm tests.
if you intend to grow the chicks for the table then you would be advised to have a coccidistat in the feed. This will have a withdrawal period for meat, this is the reason you switch to a feed without one.
If you are keeping the hens for laying then you should have the cocidiosis vaccine as mentioned above. you should also consider an infectious bronchitis, of which there are many strains, and salmonella vaccine. Infectious bronchitis can cause false layer syndrome, which means that the hen is unproductive. Salmonella i think everyone knows about. Apart from that i don't think that there is anything else, unless there is a history of endemic disease on your holding or nearby.