The Universities and Colleges Admissions Service (UCAS) publish data on applications to full time undergraduate courses at each university, which is available here: https://www.ucas.com/corporate/data-and-analysis/ucas-undergraduate-releases/ucas-undergraduate-reports-sex-area-background-and-ethnic-group/2017-entry-ucas-undergraduate-reports-sex-area-background-and-ethnic-group. This includes a measure of educational disadvantage, Participation of Local Areas (POLAR), which classifies small areas into five groups according to their level of young participation in higher education.
Information on the number of applications from each POLAR3 quintile to each Russell Group institution, and the proportion of applications that these account for, is shown in the attached table. The POLAR3 quintiles range from the group with the most disadvantaged applicants (quintile 1) through to the group with the most advantaged applicants (quintile 5).
Data is for UK domiciled 18 year olds who applied before the June application deadline through UCAS, with a known POLAR3 classification. Application numbers are rounded to the nearest five. When applying through UCAS, applicants can make up to five applications.