| Member's Company | Design | Install | Survey | Advice | Postcode |
| Gaspro Services Ltd. - Worthing | * | * | BN13 3AT | ||
| Don White Services, Belfast, County Down | * | * | BT4 3FF | ||
| Greenheat Ltd. - Cambridge | * | * | * | * | CB3 0QF |
| Dragon Building Contractors, Saffron Walden | CB10 2SS | ||||
| Clee Plumbing Ltd., Cleethorpes | * | * | DN35 0SN | ||
| Wallwork Heating Engineers, Newham | * | * | E12 6HN | ||
| Salkent Ltd., Wateringbury | * | * | ME18 5NU | ||
| Boiler Diagnostics Ltd., Snodland | ME6 5QH | ||||
| Lauder Technical Services, Airdrie | * | ML6 8QU | |||
| A. C. Heating, Didcot | * | * | OX11 5JB | ||
| Heat Plant Services, Bracknell | * | * | * | RG12 7DT | |
| Energysavers, Cadnam | * | * | * | SO40 2NL | |
| Leigh Heating & Plumbing, Leigh-on-Sea | * | * | SS9 2AY | ||
| Pegrum Heating, Tunbridge Wells | * | TN4 8PS | |||
| Heating Design Services, York | * | * | YO1 5AT |