I tried `orm.ContentType` and `orm['contenttypes.ContentType']` but neither work. I think this is because we're altering tables that have not been frozen into this migration so they're not available via `orm` ([relevant bit of docs](http://south.readthedocs.org/en/latest/ormfreezing.html)).

We could freeze in the models so that we could use `orm` but I'm already somewhat abusing South and didn't want to add more complications, especially as they probably won't change (as you say).