Yes, Essex got a 5* in both politics and economics. In terms of research, Essex is highly regarded for politics. As far as I know, in the past many people with Essex MA (some areas of politics) can get into top US Unis Phd.
Some professors in my uni (University of Hong Kong) come from Essex too (in Human rights law, Sociology etc.).
I am not going to attend Essex, so please don't give me bad rep just because Essex does not have a top general reputation.