history coursework a level

I am inclined to say that it's a secondary source, but as long as you're well-supplied with both kinds you don't need to get hung up about it. Yes you should reference statistics, because it's not your own work.

Wikipedia defines a primary source as "an artefact, document, diary, manuscript, autobiography, recording, or any other source of information that was created at the time under study." (my bold, not theirs)

The information itself would be a primary source if it were collected at the time, but the analysis of the data as a graph would be a secondary source.