Barclays typically offers loans to applicants with "Fair" (and above) credit ratings. It's important to note that your credit record is just one factor that Barclays will consider, however if you have a poor credit rating, you're very unlikely to get approved for a Barclays loan.
A "Fair" (or higher) credit rating would require a score of at least 721 if you're referring to Experian's scale, 439 if you're referring to Equifax's scale and 566 if you're referring to TransUnion's scale.