I think the problem in the UK is that this kind of work has become monopolised by gang-masters who have an interest in recruiting workers from the poorest areas

I think the problem in the UK is that this kind of work has become monopolised by gang-masters who have an interest in recruiting workers from the poorest areas of the EU. I'm not so sure there is any great shortage of willing workers at the moment but it may be a problem in the future once free-movement comes to an end? As has been mentioned about the US above, there is this myth, propagated by the media, that natives aren't interested, are too lazy and so on... Truth is that farmers have gotten away with exploiting cheap labour and they don't want it to end. You try getting a job today, as a UK native, picking vegetables and you'll likely face a brick wall. We didn't have any problems before when people could do casual seasonal work for a fair days pay. When the source of cheap labour dries up we'll likely go back to not having problems. Just a few fat farmers will be slightly miffed about it.