Credit reference agencies (CRA) hold files of your credit history. By getting a copy of your credit report it will help avoid any surprises and also give you a chance to correct any mistakes before applying.
In the UK there are three main credit reference agencies Experian, Equifax and TransUnion (formerly Callcredit).
Experian – CreditExpert
Equifax – ClearScore, CheckMyFile
TransUnion (formerly Callcredit) – Noddle, TotallyMoney, CheckMyFile
NOTE: Experian, Equifax and Callcredit scores may vary because not all lenders report to all three credit reference agencies.