Complex sentence: In December 2013 McVities announced to shop floor employees at the Harlesden plant changes from a 5 day 8 hour operation, to a 7 day 12 hour operation.
Split into simpler sentences: In December 2013 McVities announced their intention to change the terms and conditions of shop floor employees at the Harlesden plant. This change meant a move from a 5 day 8 hour operation, to a 7 day 12 hour operation.