I'm one of those lamenting UK gundog owners/trainers and have been trying for 6 months to source a couple of birds which were going to be culled. I've only ever used my birds in a non destructive manner, i.e. I don't actually harm them, the dogs just learn to push them out from grass/bushes, without physical contact (otherwise the dog has failed) then they fly back to my mini loft. Its basically to teach the dog to find and flush a bird and stop dead when they do.
So if I don't hurt them why do I need them - I've been out of training dogs for a good few years, my old stock was sold on, but now I have three new dogs, so I need some new, chaep, failed, cull stock.