| Name | Company Number | Date Appointed | Rating |
|---|---|---|---|
| Serco Metrolink Ltd | 03337055 | 23/07/2001 | Dissolved |
| Serco Nationwide Fire Services Ltd | 03306417 | 23/07/2001 | Dissolved |
| Serco Rail Services Ltd | 03119213 | 23/07/2001 | Dissolved |
| Serco Raildata Ltd | 03340203 | 23/07/2001 | Dissolved |
| WEFLEX 2 LTD | 09939252 | 09/07/2021 | Silver |
| WEFLEX 6 LTD | 15050339 | 04/08/2023 | Bronze |
| WEFLEX LTD | 09704423 | 23/06/2021 | Amber |
| Name | Company Number | Date Appointed | Date Resigned | Rating |
|---|---|---|---|---|
| BALMSOUND LIMITED | 03202175 | 10/10/1997 | 20/09/2000 | Not Trading |
| COULSTOCK & PLACE ENGINEERING CO LIMITED | 02040654 | 17/03/1997 | 21/01/1998 | Gold |
| COULSTOCK & PLACE ENGINEERING CO LIMITED | 02040654 | 17/03/1997 | 20/09/2000 | Gold |
| J & E HALL LIMITED | 03120673 | 10/10/1997 | 20/09/2000 | One Red Flag |
| MERSEYRAIL SERVICES HOLDING COMPANY LIMITED | 04620520 | 06/01/2003 | 21/10/2003 | Silver |
| Manchester Tram Co Ltd | 04183241 | 23/07/2001 | 03/04/2003 | Dissolved |
| NORTHERN RAIL HOLDINGS LIMITED | 04007719 | 09/07/2002 | 21/10/2003 | Dissolved |
| NORTHERN RAIL LIMITED | 04619954 | 06/01/2003 | 21/10/2003 | Dissolved |
| Railtest Ltd | 03302974 | 23/07/2001 | 21/10/2003 | Dissolved |
| Railtest Operations Ltd | 03318555 | 23/07/2001 | 21/10/2003 | Dissolved |
| SERCO DOCKLANDS LIMITED | 03145194 | 23/07/2001 | 15/10/2003 | Dissolved |
| Serco Merseyside Ltd | 04516383 | 30/08/2002 | 21/10/2003 | Dissolved |
| Serco Railtest Ltd | 03114741 | 23/07/2001 | 20/01/2003 | Dissolved |