Employment law does not change 'all the time'. In fact it has been pretty stable throughout the life of nu-Labour, who have not reversed most of the previous Tory policies and Acts.
Perhaps because they realised they were largely pretty sensible.
You'd be wasting yir time contacting Jobcentre Plus about employment law as it is nothing to do wi us. I always tell folk to get in touch wi ACAS as they are the experts.