Ofqual, the independent qualifications regulator, is responsible for accrediting qualifications in England and for determining their level. All Level 1 accredited qualifications (equivalent to GCSE grades D-G) and Level 2 qualifications (equivalent to GCSE grades A*-C) are listed on the National Database of Accredited Qualifications at:
http://www.accreditedqualifications.org.uk/index.aspx