I believe that the majority of Slaughter men in the UK are Muslim, as the majority of meat on sale is Halal. To quote from the Guardian - Why is there so much halal meat? 8 May 2014
"One possible answer is contained in the Daily Mail's article, when it quotes a spokesman from Compassion in World Farming:
With ever-larger abattoirs now exporting meat to wider and wider markets, it has become simpler and more cost effective for many of them to subject all their animals to halal slaughter."