Well, if it isn't going to be pulled, here's my thinking.
1) I loathe the awful generalisations that are resorted to when some people make scathing comments about people on benefits, or who are unemployed for whatever reason.
2) I don't like the underlying and unwritten suggestion that those who come here from abroad are "stealing" work from the British. They are not. See 3).
3) The booming UK soft fruit market would never have taken off without the availability of migrant labour. 100 years ago it was travellers (gypsies?) and internal migrants who did this. Now it's migrants from other countries. It's called globalisation, and in the current world it cannot be ignored.
4) A migrant agricultural worker's costs are low. They generally live in temporary accommodation, send money home to a country where costs are generally lower, and work all the hours they can to earn enough to make it worth their while being here. A local worker is most likely going to have much higher living costs, even just to keep a roof over the heads of their family. I am sure there are a lot who shun the idea of taking up temporary work just because it is hard work for little pay, but I guess there are also lots who just simply cannot afford to come off benefits to this end. I am sure I am over-simplifying things, but without further evidence this is how I see it. Most people are much the same in outlook and expectations. Some are luckier than others, but we are all just humans with an instinct to do the best for ourselves and our families.
5) Regarding employing local miners, as time moves on, there are fewer and fewer trained young miners in the UK. Little wonder that there is talk of bringing them from elsewhere - no training required, and they can hit the road running. It's a no brainer for any big business to look for the most available workforce and be less bothered about local-ism.