Hi AMy...
there wan't one major UK chocolate producer that didn't use slave labour, although the vast majoprity srongly condemned it. 
Althought the article did point out that trad sanctions only served to make life more difficult for the slaves in the short term, campaings against appartate in south affrica did prove to be sucessful when consumers changed purchasing habits against brands form this country. Within a fairly short time, the political climate did buckle and eventaully they set Nelson Mandel free. It's not a quick process but it is effective.
Interesting
Lov n hugs
Lis