Usually, the minimum band score in IELTS required for admission at British universities is 6.0 for undergraduate students and 6.5 for postgraduate students. However, there are some universities which accept students with band score below 6.0 too.
There are some universities which offer you a conditional admission if you have score below their requirements. Following are some of the universities where you may be eligible to apply:

De Montfort University
Royal Holloway, University of London
University of Central Lancashire
Leeds Metropolitan University

These are not all the universities where you can apply. To find the university where you may be eligible, please visit the website of respective universities.