Which LDZ / Local Distribution Zone you are in has a significant effect on your gas bill. This applies to both the standing charges and the unit rates or price per therm. Unfortunately, it’s also something you can’t change, short of moving your business. Your LDZ also dictates who you will need to contact to upgrade or downgrade your supply or if you are looking for a new supply.
The NT area covers the following Postcodes

Towns
Addlestone |
Amersham |
Ascot |
Ashford |
Bagshot |
Barking |
Basildon |
Beaconsfield |
Benfleet |
Billericay |
Bourne End |
Bracknell |
Brentford |
Brentwood |
Buckhurst Hill |
Camberley |
Canvey Island |
Chalfont Saint Giles |
Chertsey |
Chigwell |
Crowthorne |
Dagenham |
Edgware |
Egham |
Feltham |
Gerrards Cross |
Grays |
Great Missenden |
Greenford |
Hampton |
Harrow |
Hayes |
Hemel Hempstead |
Henley-on-Thames |
High Wycombe |
Hockley |
Hornchurch |
Hounslow |
Ilford |
Ingatestone |
Isleworth |
Iver |
Kingston Upon Thames |
Leigh-on-Sea |
Lightwater |
London |
London |
Loughton |
Maidenhead |
Marlow |
Northolt |
Northwood |
Pinner |
Princes Risborough |
Purfleet |
Rainham |
Rayleigh |
Reading |
Richmond |
Rochford |
Romford |
Ruislip |
Shepperton |
Slough |
South Ockendon |
Southall |
Southend-on-Sea |
Staines |
Stanford-le-Hope |
Stanmore |
Sunbury-on-thames |
Teddington |
Tilbury |
Twickenham |
Upminster |
Uxbridge |
Virginia Water |
Wembley |
West Byfleet |
West Drayton |
Westcliff-on-Sea |
Weybridge |
Wickford |
Windlesham |
Windsor |
Woking |
Wokingham |
Woodford Green |
Counties
Middlesex |
Oxfordshire |
City of London |
Berkshire |
Buckinghamshire |
Surrey |
Essex |
The NT Distribution Zone is operated by Cadent