I use a homeopathic wormer for all my livestock. I get it from Ainsworths. So simple just mix & spray on their nose, in water for hens.
Though if there were any problem that this didn't work for I would use a conventional wormer.
Animals always come first
My wife and I have used Homeopathic methods of worming both of us but it has to be done over a long period of days in water, just before meal times. Here is how it went: The first week take 10 drops 3 times a day. The second week take 20 drops 3 times a day. Third week take 30 drops every other day. How the dickens was I ever going to complete that. Not on your nelly. Needless to say it never got completed.
It would be interesting to see if spraying it on there noses works. Only one way to know and that by sending in a dung sample. Free check here surely S&S.
Ivermectin is good and covers Mange, Lice and worms but has a 28 day withdrawal, Panacur has only 10, but there is a product called Wormtec that has 0 withdrawal days. I have never used it and am not sure whether it is available or legal in the UK, but it would be an ideal option if after getting samples checked, if that is what is needed to be done.