The University of Essex is respected, it's not Russell group but in specific research subject areas it ranks quite high.
Whether employers rank it highly is another matter, most employers care more about what you studied and what relevant work experience you have than where you studied. The ones that specify say Russell group universities, tend to also expect good A levels and GCSEs, in other words a consistent academic record. If the university you attend has good links with employers you want to work for, this is more useful.