AFAIK Morrisons take on people under the UK workfare scheme (so that those in question receive only the benefits they would otherwise receive, not a proper wage, but are obliged to work 40 hours per week - or it might be 30 hours per week). They pretend that those taken on receive training. I did challenge this on their facebook page and they did not deny it although they did try to justify it. As a result I now shop at ALDI LIDL or Sainsbury's since there is no useful nearby Waitrose.

Tesco also use this sort of slave labour, likewise ASDA, so there's no point in switching to them if you want to do ethical shopping.

I am very reluctant to use Amazon, and will only do so if I cannot source something I want elsewhere. I'm doing well for second-hand DVDs on ebay at the moment, and saving money too.