Details of Ofgem approved meters can be found at:
Schedule 4 of Statutory Instrument 1998 No.1566 - The Meters (Certification) Regulations 1998 - PDF, 553KB - opens in a new document window
From 30 October 2006, all new designs of gas and active electrical energy meters must conform to the requirements of the Measuring Instrument Directive (MID) in order to be used across the EU (including UK) for trade purposes (i.e. billing). The MID replaces the former requirements under the GB Electricity Act 1989 and the Gas Act 1986.
Ofgem no longer approves or certifies new electricity meters for use under 100kW or gas meters, and Notified Bodies, designated by EU member States, now undertake this role.