you could ask a local with ferrets to come and sort them out, or you could use live traps .. they cost about £20 each , but will last for many years . With live traps you then have to decide what you are going to do with them if you catch any ? Break their necks or let them go on someone else's land ? The ferret man will most likely keep what he catches , but they normally give you some if you want them . I hate snares so never advise anybody to use them . You could end up catching one of your own dogs or someone else's , or even a cat . Whatever , it is a horrible way to kill them . Poison is out too as you have dogs , if you have a big area you could try your local falconer, someone with a Harris hawk would be able to help . But they need plenty of room to work in . Then you have air rifles . If you can sit there for hours on end , hiding under cover , you may see one , but nearly always just out of range !! You could also ask someone with a lurcher to take their dog walkies by your plot , if you have plenty of flat space ? Out of all those I would say the ferret man would be the best choice . They will clear large numbers in one go , and come back on a regular basis if you want them too.....
cheers
Russ