This is by no means official or published, but these tiers have been made by many UCAS Supervisors in various schools and colleges, including mine and 9 other schools/colleges within North London.
What are your thoughts?
Tier 1
University of Cambridge
University of Oxford
London School of Economics and Political Science
Imperial College London
University College London
Kings College London
Tier 2
University of Bristol
University of Warwick
University of Durham
University of Exeter
University of Southampton
University of Nottingham
University of Birmingham
University of Manchester
University of Edinburgh
University of Leeds
University of Glasgow
Queen Mary University of London
Tier 3
University of Cardiff
University of Newcastle
University of Sheffield
Queen's Belfast University
University of Liverpool
University of York
Universities that UCAS Supervisors believe should be in the Russel Group:
-University of Surrey
-St. Andrews University
-University of Bath
-University of Loughborough
-University of Lancaster