Sometimes universities not in the Russell Group are as good as those in it. Lancaster, Bath and St Andrews being examples. I believe Cardiff dont require A level Maths for Economics and they are RG university. From memory I think Nottingham, Lancaster, Liverpool, Newcastle, East Anglia, Reading, Royal Holloway, Kent and Sussex dont but you might need to check these. They are all excellent universities and most are either RG or former 1994 group universities. Many are Sutton Trust universities.